1. Introduction and Key Terminology
An electoral system is the mechanism by which votes cast in an election are converted into seats in a legislature, or into a single office such as a mayoralty. The choice of system is not neutral: it shapes which parties can realistically win power, how governments are formed, how voters behave, and how closely the outcome reflects the wishes of the electorate. The United Kingdom does not use a single electoral system; different systems operate concurrently for Westminster, the devolved parliaments, London, and local government.
Three families of system
Plurality systems award victory to whoever wins the most votes, even well short of 50 per cent. The UK’s First Past the Post (FPTP) system is, strictly, a plurality system, though textbooks conventionally group it with majoritarian systems because both manufacture a decisive winner rather than mirror the electorate.
- Majoritarian systems require an absolute majority (50 per cent plus one) to win, usually via a second round of voting or a preferential ballot with elimination rounds. The UK does not currently use a true majoritarian system for any major election, though the Alternative Vote (AV) was rejected by 67.9 per cent to 32.1 per cent in a 2011 referendum.
- Proportional representation (PR) systems aim to allocate seats to parties in close proportion to their vote share. There is no single PR system: the family includes Closed List PR, the Single Transferable Vote (STV), and hybrid systems such as the Additional Member System (AMS), internationally known as Mixed Member Proportional (MMP).
2. First Past the Post (FPTP)
Mechanics
- The country is divided into 650 single-member constituencies for Westminster (the same principle applies to most English local council wards).
- Voters mark a single cross against one candidate.
- The candidate with the most votes wins, regardless of whether they reach 50 per cent.
- The party with the most seats overall usually forms the government, alone or, if no party reaches a majority, through coalition (2010) or confidence-and-supply arrangements (2017).
Where it is used
- UK general elections, electing MPs to the House of Commons.
- English local council elections.
- Directly elected mayors in England, including the Mayor of London, which reverted to FPTP from the Supplementary Vote under the Elections Act 2022.
Strengths
- Simplicity: a single cross for voters, and fast counting for officials.
- A strong constituency link, since every elector has one identifiable, accountable MP or councillor.
- Tends to produce decisive, single-party majority government.
- Raises the effective threshold against small or extreme parties, since winning a seat requires concentrated local support.
Weaknesses
- High disproportionality between a party’s vote share and its seat share.
- Wasted votes: ballots cast for losing candidates, or surplus votes above the winning margin, have no effect on the result.
- Safe seats: many constituencies do not change hands for decades, which critics argue depresses turnout and campaign effort.
- Tactical voting: electors often back their preferred candidate’s strongest rival rather than expressing a sincere first preference.
- Rewards geographically concentrated support (for example the SNP, or Liberal Democrat target seats) and punishes support that is spread evenly across the country (Reform UK, the Green Party).
- Duverger’s Law: plurality systems tend to compress competition into two dominant parties, though the 2024 result has renewed debate about whether this pattern is weakening in the UK.
Evidence: the 2024 general election
| Party | Vote share | Seats won | Seat share |
| Labour | 33.7% | 411 | 63.2% |
| Conservative | 23.7% | 121 | 18.6% |
| Reform UK | 14.3% | 5 | 0.8% |
| Liberal Democrat | 12.2% | 72 | 11.1% |
| Green | 6.7% | 4 | 0.6% |
| SNP | 2.5% (UK-wide) | 9 | 1.4% |
- Labour won a majority of 174 seats on barely a third of the national vote, widely described as the most disproportionate result on record.
- Reform UK won almost 4.1 million votes, more than several other parties combined, but only five seats, because its support was spread evenly rather than concentrated.
- An estimated 58 per cent of votes cast in 2024 did not contribute to the result (were “wasted”).
3. The Additional Member System (AMS)
Mechanics
- A hybrid of FPTP and PR. Voters cast two votes: a constituency vote (decided by FPTP) and a regional list vote.
- Regional list seats are allocated using the D’Hondt formula, which compensates parties under-represented by the constituency results relative to their regional vote share.
Where it is used
- The Scottish Parliament (Holyrood).
- The London Assembly.
- Wales used AMS for the Senedd from 1999 to 2021, before moving to Closed List PR (see Section 5).
Strengths
- Combines a local constituency representative with overall proportionality.
- Allows split-ticket voting: a local candidate from one party, a regional vote for another.
- Reduces wasted votes relative to FPTP.
- Encourages consensus politics rather than single-party dominance.
Weaknesses
- Creates two tiers of representative: constituency members with a local mandate, and list members without one.
- Party leaderships control list ordering, giving them significant influence over who is elected.
- Parties can attempt to “game” the regional calculation through separate list vehicles.
- The D’Hondt calculation is less transparent to voters than simple plurality counting.
Evidence: Scotland 2026 (actual AMS result)
| Party | AMS seats (of 129) | Constituency vote share |
| SNP | 58 | 38.2% |
| Reform UK | 17 | 15.8% |
| Scottish Labour | 17 | 19.2% |
| Scottish Greens | 15 | ~2.3% |
| Scottish Conservatives | 12 | ~12.0% |
| Scottish Liberal Democrats | 10 | ~10.0% |
- The SNP remained the largest party but fell seven seats short of a majority (65 needed), requiring First Minister John Swinney to lead a minority administration.
- Six parties won representation, illustrating AMS’s semi-proportional character.
4. Single Transferable Vote (STV)
Mechanics
- Used in multi-member constituencies, typically returning three to six representatives.
- Voters rank candidates in order of preference (1, 2, 3, and so on).
- Candidates must reach the Droop Quota to be elected: Quota = (Total valid votes ÷ (Seats available + 1)) + 1.
- Candidates exceeding the quota on first preferences are elected, and their surplus votes are transferred according to next preferences. If no candidate meets the quota, the lowest-placed candidate is eliminated and their votes redistributed. The process repeats until all seats are filled.
Where it is used
- The Northern Ireland Assembly.
- Local government elections in Scotland and Northern Ireland.
- Comparative note: used nationally in the Republic of Ireland.
Strengths
- Maximum voter choice: electors can rank candidates within or across parties, or support independents.
- High proportionality without handing party leaderships control over list order.
- Eliminates safe seats, since candidates from the same party must compete against one another for preferences.
- Encourages candidates to seek transfers from outside their core base, promoting cross-community moderation, notably in Northern Ireland.
Weaknesses
- A complex counting process involving multiple rounds of quota calculation and transfer, which can take days to resolve.
- A diluted local link, since multi-member constituencies are geographically larger and shared between several representatives.
- Intra-party rivalry, as party colleagues compete against one another for first preferences.
- Can produce fragmented assemblies requiring protracted coalition negotiation.
Evidence: Northern Ireland Assembly, May 2022
- 90 MLAs were elected across 18 multi-member constituencies (5 seats each).
- Sinn Féin became the largest party with 27 seats on 29.0 per cent of first-preference votes.
- The cross-community Alliance Party rose to 17 seats from just 13.5 per cent of first preferences, by attracting transfers from both nationalist and unionist voters, illustrating STV’s capacity to reward consensus-building.
5. Closed Proportional List
Mechanics
- Multi-member regions elect several representatives.
- Parties publish a pre-ordered list of candidates before polling day.
- Electors vote for a party, not an individual candidate.
- Seats are allocated to parties in proportion to regional vote share (again, typically the D’Hondt formula), and filled strictly in the order set by the party.
Where it is used
- Senedd Cymru (the Welsh Parliament), following the Senedd Cymru (Members and Elections) Act 2024.
- Historically, UK elections to the European Parliament, until Brexit.
Strengths
- Near-exact proportionality between vote share and seat share.
- Very simple for voters: a single choice of party.
- Fair to smaller parties that cross the regional threshold.
- Allows parties to structure lists for demographic balance, such as gender.
Weaknesses
- Severs the link between a representative and a specific local area.
- Places candidate selection entirely in the hands of party leaderships.
- No ability for voters to choose between individual candidates within a party.
- Small parties can gain disproportionate leverage in coalition bargaining.
Evidence: Senedd Cymru, May 2026
- The Senedd was enlarged to 96 members, elected across 16 six-member constituencies.
- Plaid Cymru became the largest party for the first time since devolution began, with 43 seats on 35.4 per cent of the vote.
- Reform UK entered the Senedd for the first time, becoming the second-largest party with 34 seats on 29.3 per cent.
- Welsh Labour fell to third place with 9 seats, the first Senedd election in which Labour has not been the largest party.
- The Electoral Reform Society’s Loosemore-Hanby disproportionality score for the result was 15.5, against 47.4 for the equivalent 2024 Westminster result in Wales, a useful concrete figure for showing that PR narrows the gap between votes and seats.
6. The UK’s Mixed Electoral Landscape
| Institution | System used |
| UK Parliament (Westminster) | FPTP |
| Scottish Parliament | AMS |
| Senedd Cymru (Welsh Parliament) | Closed List PR since 2026 (AMS 1999-2021) |
| Northern Ireland Assembly | STV |
| London Assembly | AMS |
| London Mayor, other English mayors, PCCs | FPTP (reverted from Supplementary Vote, 2022) |
| Local councils, England | FPTP |
| Local councils, Scotland and Northern Ireland | STV |
This patchwork allows a natural experiment: broadly the same electorate and party system produce different outcomes depending on the electoral rule applied, which is useful evidence for evaluation essays.
7. Counterfactual Case Studies: What if the System Had Been Different?
Scotland 2026: AMS versus a hypothetical FPTP
- Under the actual AMS result, six parties won seats and the SNP formed a minority government, seven seats short of a majority.
- Modelling the same constituency-level votes under FPTP (73 single-member seats) would have given the SNP 57 seats (78.1 per cent) from just 38.2 per cent of the constituency vote, an outright majority.
- Reform UK (15.8 per cent of the vote) would have won 0 constituency seats under FPTP, against the 17 seats it actually won via the regional list.
- Scottish Labour (19.2 per cent) would have fallen to 2 seats under FPTP, rather than the 17 it actually won.
- Judgement: AMS produced the more representative outcome, since it aligned seats more closely with vote share and avoided a large “manufactured majority” for the SNP.
Wales 2026: Closed List versus a hypothetical FPTP
- Under the actual Closed List result, Welsh Labour won 41 of 96 seats, 8 short of a majority, requiring cross-party cooperation.
- Modelling the same voting patterns under FPTP (96 single-member seats) would have given Welsh Labour an estimated 68 seats (70.8 per cent) from around 35 per cent of the vote.
- Reform UK (an estimated 16 per cent of the vote) would have won just 1 seat under FPTP, against the 14 it actually won under the Closed List.
- Judgement: as in Scotland, the proportional system produced the outcome more closely aligned with actual public support, at the cost of requiring coalition or cross-party negotiation to govern.
The 2024 general election, modelled under PR
A note on methodology: this is informed estimation, not genuine alternative history. Under a different system, parties would field different candidates, campaigns would differ, and voters freed from the incentive to vote tactically (around a third of 2024 voters said they had) might have voted differently in the first place. The figures below come from the Electoral Reform Society, “A System Out of Step: The 2024 General Election” (December 2024). The ERS is a campaigning organisation for electoral reform, so its figures are worth reading with that advocacy position in mind; its modelling used a YouGov poll of voters’ preference rankings, rather than simply reallocating raw FPTP votes.
| Party | Actual (FPTP) | STV | AMS (50:50) | AMS (68:32) | List PR |
| Labour | 411 | 227 | 228 | 282 | 194 |
| Conservative | 121 | 148 | 139 | 134 | 147 |
| Liberal Democrats | 72 | 71 | 73 | 58 | 78 |
| Reform UK | 5 | 90 | 100 | 75 | 109 |
| Green Party | 4 | 67 | 71 | 57 | 83 |
| SNP | 9 | 16 | 16 | 18 | 16 |
| Plaid Cymru | 4 | 8 | 4 | 5 | 5 |
- Labour’s majority disappears under every modelled variant. Even the least proportional model tested, AMS (68:32), gives Labour only 282 seats, short of the 326 needed.
- Reform UK’s seat total rises to somewhere between 75 and 109, broadly proportionate to its 14.3 per cent vote share, compared with 5 actual seats.
- A genuinely multi-party Commons emerges in every scenario; the ERS suggests the likeliest outcome would be a Labour-led coalition with the Liberal Democrats and/or the Greens, against a divided right of Conservatives and Reform UK.
- The specific proportional system chosen still matters: moving from AMS (50:50) to AMS (68:32) alone shifts around 54 seats towards Labour, a reminder that “PR” is a spectrum rather than a single outcome.
8. The FPTP versus PR Debate: Who Argues What, and Why
Political parties
- Conservative Party: the strongest institutional defender of FPTP, emphasising stable single-party government and the constituency link. Critics note the Conservatives have directly benefited from FPTP’s disproportionality, for example 43.6 per cent of the vote producing a comfortable majority in 2019.
- Labour Party: historically ambivalent, having benefited from FPTP landslides in 1997, 2001 and 2024, though a significant and growing faction, including affiliated trade unions, has passed conference motions favouring PR.
- Liberal Democrats: the most consistent advocates of reform, specifically STV, on grounds of fairness. In 2015, the Liberal Democrats and UKIP together won around a quarter of the vote but a tiny fraction of seats.
- Smaller and regional parties (the Green Party, Reform UK, Plaid Cymru): strong advocates of PR, since their support is dispersed rather than concentrated. The SNP is a partial exception: FPTP has worked in its favour in Scotland (56 of 59 Scottish seats on 50 per cent of the Scottish vote in 2015), so its enthusiasm for reform is more selective, and tends to focus on Scottish independence.
Pressure and interest groups
- Make Votes Matter and the Electoral Reform Society campaign for a proportional Westminster system, arguing FPTP produces unrepresentative governments, encourages tactical voting, and creates safe seats where turnout and engagement fall. The Electoral Reform Society has campaigned for reform since 1884.
- Fairer Vote and Unlock Democracy connect electoral reform to wider concerns about political disengagement, especially among younger voters, arguing a vote in a safe seat can feel meaningless.
- Defenders of FPTP, including some constitutional think tanks, argue that its simplicity and clear accountability outweigh its disproportionality, pointing to coalition or minority government in more proportional systems such as Germany or Israel as evidence that PR can produce weak or unstable government.
The press
- Right-leaning outlets (the Daily Mail, The Telegraph, The Sun) generally defend FPTP, echoing arguments about stability and the constituency link, and often frame PR as risking “coalition chaos”.
- Left-leaning and centrist outlets (The Guardian, The Independent, The Mirror) are more sympathetic to reform, with The Guardian giving particular attention to disproportionality and wasted votes, especially after skewed results such as 2015 and 2024.
- Broadcasters (the BBC, Sky News, ITV) are bound by Ofcom impartiality rules and present both sides of the debate more evenly, particularly around election results and referendum moments such as the 2011 AV referendum.
Key evaluative point for essays
- Positions in this debate are rarely held on principle alone. Parties and pressure groups tend to support whichever system best serves their own electoral prospects, which is a valuable point for interrogating stated motives rather than taking them at face value.
9. A Comparative Case: The United States
- The House of Representatives is elected via single-member plurality districts, functionally similar to FPTP, producing a two-party system arguably even more rigidly entrenched than the UK’s, since minor parties almost never win federal seats.
- Gerrymandering, the deliberate manipulation of district boundaries by state legislatures to advantage one party, is a distinctly American aggravation of the disproportionality inherent in plurality systems.
- The Senate is not proportional to population at all: every state elects two senators regardless of size, so California (around 39 million people) has the same representation as Wyoming (around 580,000). This is a deliberate federal design feature rather than a proportionality failure.
- The Electoral College, which formally elects the President, is a largely winner-takes-all, state-based system: in 48 of 50 states, all of that state’s electoral votes go to whoever wins its popular vote, however narrow the margin. This has twice produced a president who lost the national popular vote, George W. Bush in 2000 and Donald Trump in 2016, arguably a more extreme distortion than anything produced by UK FPTP, since it can invert the national result entirely.
- Comparing the UK and US cases shows that plurality logic produces broadly similar effects (two-party dominance, safe versus competitive seats, disproportionality) wherever it is applied, but the severity depends on surrounding institutional design, such as how district boundaries are drawn and controlled, and whether the system sits within a federal structure.
10. Evaluation Framework
| Criterion | FPTP / majoritarian systems | PR systems |
| Proportionality of votes to seats | Weak; can produce landslide majorities from a minority of the vote | Strong, varies by type (list PR strongest, AMS semi-proportional) |
| Government stability and decisiveness | Usually strong; single-party majorities more likely | Weaker; coalition or minority government more common |
| Voter choice | Limited to one cross; little intra-party choice | Greater under STV and open list; limited under closed list |
| Simplicity for voters | Very simple | Varies; STV and list systems more complex than FPTP |
| Constituency accountability | Strong; single named MP | Varies; strong under STV/AMS, weak under closed national list |
| Representation of smaller parties | Poor | Good, subject to any threshold |
| Risk of extremist representation | Low (high effective threshold from local plurality) | Higher without a formal vote threshold |
| Government mandate clarity | High: governing party’s manifesto usually enactable | Lower: coalition agreements often dilute manifesto commitments |
No system performs well against every criterion simultaneously. This trade-off, rather than a single “correct” answer, is the central analytical point that examiners reward in evaluation.
11. Conclusion
- The underlying tension is between decisiveness and accountability on one side, and fairness and representativeness on the other.
- FPTP delivers simple, usually stable, single-party government with clear accountability, at the cost of significant, sometimes extreme, distortion between votes and seats, as the 2024 general election illustrates starkly.
- PR systems correct that distortion and better reflect a pluralistic, multi-party society, but generally produce coalition or minority government and, in some variants, dilute the direct constituency link.
- The UK’s own experience, running FPTP at Westminster alongside AMS in Scotland, Closed List PR in Wales, and STV in Northern Ireland, offers a built-in comparison for exam answers, while the American case shows how majoritarian logic can produce even sharper distortions when layered onto a federal structure.
- There is no electoral system that is neutral among these values: the choice of system is, in effect, a choice about which democratic values a political system prioritises.