Electoral systems

First-past-the-post (FPTP) is used to elect the 650 MPs in the House of Commons. Each constituency elects one MP; voters mark one ‘X’ and the candidate with the most votes wins, whether or not they have a majority. It is a plurality, not a majority, system: in 2024, according to the Electoral Reform Society (a campaign group), 554 of the 650 seats (85%) were won by a candidate with less than half of the local vote, and 266 (41%) with less than 40%.^[3][4]

The Additional Member System (AMS) is a mixed system used for the Scottish Parliament (and for the Senedd until 2021). Each voter has two votes. The first elects a constituency member by FPTP in 73 constituencies; the second is for a party list in one of eight regions, each electing seven members, giving 56 regional seats. Regional seats are shared out using the d’Hondt formula, which takes into account the constituency seats each party has already won, so the list ‘tops up’ parties that did badly in the constituencies.^[5]

The Single Transferable Vote (STV) is used for the Northern Ireland Assembly, where 18 constituencies each elect five members, and for Scottish local council elections since May 2007. Voters rank candidates in order of preference (1, 2, 3…). A candidate who reaches a quota of votes is elected; their surplus votes, and the votes of the candidate in last place who is eliminated, are transferred to the voters’ next preferences until all seats are filled.^[6][7]

The Closed Proportional List System (CPLS) was used for the first time in the Senedd election of 7 May 2026, replacing AMS. The Senedd grew from 60 to 96 members, elected in 16 constituencies of six members each. Voters cast one vote for a party list (or an independent candidate); seats are allocated by d’Hondt and filled in the order the party has ranked its candidates. Voters cannot choose between candidates on a party’s list, which is why it is called ‘closed’. Vacancies are filled from the list, so there are no by-elections.^[8][9]

These systems sit on a spectrum. FPTP is a majoritarian system that tends to reward the largest parties; STV and list systems are proportional; AMS is a hybrid that combines a constituency link with a proportional top-up. In practice even the proportional systems are not perfectly proportional, as the 2026 Scottish and Welsh results showed.^[10][11]

Figures in this table come from the 2024 general election, the 2026 Scottish and Welsh elections and the 2022 Northern Ireland Assembly election. Use the Power Map tab to see how these systems translate into seats in each legislature.^{[4][12][10][6][13]}

The clearest way to compare systems is to look at how far each party’s share of seats matches its share of votes. Political scientists often use the Gallagher index, where 0 means perfectly proportional and higher scores mean more disproportional. The Electoral Reform Society (a campaign group for proportional representation) calculated that the 2024 general election scored 23.6, the highest on record, beating the previous peak of 20.6 in 1983.^[4]

Westminster 2024 (FPTP): Labour won 411 seats on 33.7% of the vote. The number of votes needed to elect one MP varied enormously: about 23,600 for each Labour MP, 56,400 for each Conservative, 48,900 for each Liberal Democrat, 486,000 for each Green and 823,500 for each Reform UK MP. The ERS estimated that 73.7% of votes (21.2 million) did not help elect anyone or were surplus to what the winner needed.^[4][3]

Senedd 2026 (CPLS): Plaid Cymru won 43 of 96 seats (44.8%) on 35.4% of the vote, and Reform UK 34 seats (35.4%) on 29.3%. Labour (11.1% of the vote, 9 seats), the Conservatives (10.7%, 7 seats), the Greens (6.7%, 2 seats) and the Liberal Democrats (4.5%, 1 seat) were all under-represented. Senedd Research put the Gallagher index at 9.5, far lower than Westminster in 2024 but only slightly better than the 10.1 recorded under AMS in 2021.^[10]

Scottish Parliament 2026 (AMS): the SNP won 57 of the 73 constituency seats on 38.2% of the constituency vote. Because the regional list could not fully compensate other parties, the SNP finished with 58 of 129 seats (45%) on 27.2% of the list vote. Reform UK won all 17 of its seats from the list, on 16.6% of the regional vote. Political scientist Chris Hanretty noted that on the Gallagher measure this was the most disproportional Holyrood election yet; Unlock Democracy, a campaign group, put the index at 13.7.^[12][14][11]

The comparison suggests that the devolved systems are much more proportional than FPTP, but not perfectly so. AMS loses proportionality when one party dominates the constituency seats, and the closed list in Wales uses fairly small six-member constituencies, which favour the larger parties. A balanced answer should therefore compare degrees of proportionality rather than treating ‘FPTP versus PR’ as a simple contrast.^[14][13]

A referendum is a vote in which the electorate answers a single question, usually with a choice between two options. There is no general legal requirement in the UK to hold a referendum on constitutional change, but some laws require one: for example, the Northern Ireland Secretary must call a referendum on Irish unification if it seems likely a majority would vote for it.^[15]

Since 1997 most referendums have been about the constitution. The Labour government elected in 1997 used them to approve devolution to Scotland, Wales, London and Northern Ireland, giving the new bodies popular legitimacy. Later referendums asked about the voting system (2011), Scottish independence (2014) and EU membership (2016). Local referendums have also been held, for example on directly elected mayors.^[15][16][17]

Referendums in the UK are not legally binding because Parliament is sovereign, but they carry great political weight. After the 2016 vote David Cameron said the people’s ‘will must be respected’ and announced he would step down as Prime Minister. In January 2017 the Supreme Court ruled, by eight justices to three, that the government still needed an Act of Parliament before starting the formal process of leaving the EU.^[18][19]

The Supreme Court ruled unanimously in November 2022 that the Scottish Parliament could not legislate for a second independence referendum without Westminster’s agreement. It noted that even a referendum with no immediate legal effect ‘would be a political event with important political consequences’. Turnout and results for each referendum are shown in the timeline below; see the Voter Profile tab for turnout trends.^[20]

The impact of these referendums has been large. The devolution votes created new institutions and electoral systems; the 2011 AV vote took Westminster electoral reform off the main parties’ agenda for more than a decade; the 2014 vote did not settle the independence question; and the 2016 vote led to a change of Prime Minister, years of parliamentary conflict and the UK’s departure from the EU. The Constitution Unit notes that referendums can legitimise major decisions but can also leave results that are hard for representative institutions to deliver.^[15][18]

For: referendums are a form of direct democracy that lets citizens decide fundamental questions themselves. They can give a decision strong legitimacy between elections, especially on constitutional issues such as devolution, and the public generally supports their use for such questions.^[15]

For: high turnout can show real engagement. The 84.6% turnout in the 2014 Scottish independence referendum was a record, and 72.2% voted in the 2016 EU referendum, well above the 2024 general election turnout.^[24][25][4]

Against: complex questions are reduced to a simple choice; campaigns can increase polarisation; and the quality of information voters receive can be poor. Ambiguous results, such as a vote to leave the EU without a defined plan for how, can be hard for MPs to put into practice.^[15]

Against: low turnouts can undermine legitimacy. The Greater London Authority was approved on a 34.1% turnout and Welsh devolution in 1997 by a margin of 0.6 percentage points. Critics also argue that governments decide whether and when to hold referendums, and on what question, often for party advantage.^[16]

The tension is with representative democracy: Parliament is sovereign and MPs are elected to weigh evidence and make judgements, yet once the public has voted it is politically very difficult for MPs to ignore the result. The Constitution Unit’s Independent Commission on Referendums (2018) concluded that referendums are valuable but should complement, not replace, representative and deliberative institutions, and must be run fairly.^[15][18]

The UK has no single principle for choosing electoral systems; each was chosen for a particular purpose. FPTP has been kept for Westminster because it is traditional, simple and tends to produce single-party government, and both Labour and the Conservatives have benefited from it. The Conservatives’ 2024 manifesto backed keeping FPTP, and the IfG noted little appetite for wholesale reform in either of the two largest parties.^[26][27]

For the devolved bodies, proportional systems were chosen to encourage consensus and to stop one party dominating. Legal scholar Aileen McHarg noted that AMS was adopted in Scotland precisely because of Labour’s overwhelming dominance under FPTP. In Northern Ireland, STV supports power-sharing between communities after the Good Friday Agreement. In Wales the Senedd chose a closed list in 2024, alongside a larger chamber, and the ERS argued STV should have been used instead.^{[28][21][8][29]}

Mayoral elections show how political the choice can be. The Elections Act 2022, passed under the Conservative government, replaced the supplementary vote with FPTP for the Mayor of London, other elected mayors and police and crime commissioners. The Labour government’s English Devolution and Community Empowerment Act 2026, which received royal assent on 29 April 2026, restored the supplementary vote for mayoral and police and crime commissioner elections. The six local authority mayoral elections on 7 May 2026 were held under FPTP because the change came too late.^[30][31][32]

Public opinion has moved towards change. The British Social Attitudes survey found in 2024 that 60% wanted to change the voting system for general elections, compared with 36% who wanted to keep it. YouGov polling in January 2026 found 45% preferred PR and 25% FPTP, but support for PR among Reform UK voters had fallen by around ten points (from 55–56% in 2025 to 45%) as Reform’s strong poll position made FPTP look more helpful to the party.^[33][34]

In 2025–26 reform stayed on the agenda. Andy Burnham, who has publicly backed PR since around 2021, became Labour leader on 17 July 2026 and Prime Minister on 20 July. In September 2026 an amendment to the Representation of the People Bill, tabled by Labour MP Alex Sobel and signed by 193 MPs, called for a National Commission to examine alternatives to the voting system but was ruled outside the Bill’s scope. The democracy minister said Burnham remained committed to electoral reform but that it was ‘premature to legislate now for one approach’. The Bill itself would lower the voting age to 16 and introduce more automatic voter registration rather than change the voting system. Then, in his Labour conference speech on 29 September 2026, Burnham announced a National Commission on Electoral Reform and said Labour would fight the next general election with a manifesto commitment to change the electoral system; the government did not say which system it favoured or whether a referendum would be held.^{[35][36][37][38][39][40]}

Type of government. FPTP usually produces single-party majority governments, but not always. There have been three hung parliaments since 1945 (February 1974, 2010 and 2017). In 2010 the Conservatives and Liberal Democrats formed a coalition that lasted the full 2010–15 Parliament; in 2017 the Conservatives governed as a minority with a confidence and supply agreement with the DUP.^[41]

Proportional systems make coalition and minority government more common. In Scotland the SNP has governed as a minority (2007–11 and 2016–21), had a majority of 69 seats in 2011, and from August 2021 to April 2024 governed with the Greens under the Bute House Agreement. After 2026 both devolved governments are minorities: John Swinney’s SNP government (seven seats short of a majority) and Rhun ap Iorwerth’s Plaid Cymru government, which must win support from other parties vote by vote.^{[42][28][5][9]}

Party representation. FPTP rewards parties whose support is concentrated geographically and punishes those whose support is spread thinly. In 2024 the Liberal Democrats won 72 seats on 12.2% of the vote while Reform UK won 5 on 14.3%. Proportional systems give smaller parties a fairer share: Reform UK won 17 MSPs and 34 Senedd members in 2026, and the Greens 15 MSPs.^{[3][4][12][9]}

Safe and marginal seats. Under FPTP, elections are decided in marginal seats. The 2024 election made seats much less safe: 115 seats had a majority under 5%, 48 more than in 2019, and only 5 had a majority above 50%, down from 37. Labour won Hendon by just 15 votes. Even so, 111 seats had been held by the same party for over a century before 2024, and 46 of them changed hands.^[43][4]

Voter choice. FPTP gives each voter one ‘X’ for one candidate, encouraging tactical voting. AMS gives two votes and allows split-ticket voting; STV lets voters rank candidates within and across parties; the closed list gives a single vote but no choice of candidate. Two-party dominance has weakened under FPTP: Labour and the Conservatives together won only 57.4% of the vote in 2024.^[4][29][6]