Electoral System

Introduction

The United Kingdom employs a variety of electoral systems for different elections, reflecting the asymmetrical nature of its constitutional arrangements. The first-past-the-post (FPTP) system is used for elections to the House of Commons, while proportional systems are used for elections to the devolved legislatures, the London Assembly, and for English local government. The diversity of electoral systems within the UK is unusual by comparative standards and reflects both historical tradition and deliberate constitutional choice. The system is overseen by an independent Electoral Commission, which regulates electoral administration, party financing, and campaign conduct.

First-Past-the-Post for the House of Commons

The first-past-the-post (FPTP) system, also known as simple plurality voting, is used for elections to the House of Commons. The UK is divided into 650 constituencies, each returning one MP. Voters cast a single vote for their preferred candidate, and the candidate with the most votes wins, regardless of whether they achieve an absolute majority. The system has several well-documented characteristics. It tends to produce single-party majority governments even where the winning party receives well under 50% of the national vote. It creates a disproportional relationship between votes and seats: smaller parties with geographically dispersed support (such as the Liberal Democrats and the Green Party) are systematically underrepresented, while parties with concentrated regional support (such as the Scottish National Party) may be overrepresented. The system also tends to exaggerate swings—a moderate shift in votes can produce a large shift in seats, enabling decisive changes of government. Proponents argue that FPTP provides strong and stable government, maintains the constituency link between MPs and their local areas, and gives voters the ability to remove an underperforming government decisively.

Proportional Systems for Devolved Elections

The devolved legislatures use proportional electoral systems that produce more representative outcomes. The Scottish Parliament and the Senedd Cymru use the additional member system (AMS) , a mixed-member proportional model. Under AMS, voters cast two votes: one for a constituency member (FPTP) and one for a regional or top-up list. Regional seats are allocated to achieve a more proportional overall outcome, compensating for disproportionality in the constituency results. The AMS system for the Senedd was reformed by the Senedd Cymru (Members and Elections) Act 2024, which moved to a wholly proportional closed-list system and increased the number of Members of the Senedd to 96. The Northern Ireland Assembly uses the single transferable vote (STV) system, under which voters rank candidates in order of preference in multi-member constituencies. Candidates reach a quota (the Droop quota) and surplus votes are transferred to remaining candidates. STV produces highly proportional results and allows voters to choose between candidates within the same party.

European Elections and Local Government

Before the UK’s withdrawal from the European Union, elections to the European Parliament were conducted using a regional closed-list system, with the UK divided into twelve electoral regions (including Scotland, Wales, and Northern Ireland). Seats were allocated proportionally using the d’Hondt formula. For English local government, the system varies: unitary authorities and metropolitan boroughs are usually elected by FPTP (by thirds or all-out), while some councils use the whole-council system. London boroughs are elected by FPTP every four years. Police and Crime Commissioners are elected by the supplementary vote system (a form of preferential voting). The Combined Authority Mayors (such as the Mayor of London and metro mayors) are also elected by the supplementary vote system. The variety of electoral systems used across different tiers of government is a distinctive feature of the UK’s constitutional landscape.

Boundary Reviews

The Boundary Commissions for England, Scotland, Wales, and Northern Ireland are independent, non-departmental public bodies responsible for keeping constituency boundaries under review. The Commissions are established by the Parliamentary Constituencies Act 1986 (as amended by the Parliamentary Voting System and Constituencies Act 2011). They conduct periodic reviews to ensure that constituencies are of roughly equal size, reflecting population movements. The 2011 Act introduced a requirement for constituencies to have electorates within 5% of the quota (the UK average electorate per constituency), with only limited exceptions for geographical factors (such as the Isle of Wight and Orkney and Shetland). This requirement was modified by the Parliamentary Constituencies Act 2020, which retained the 5% target but allowed greater flexibility. The 2023 Boundary Review was conducted on the basis of 650 constituencies and resulted in significant changes to constituency boundaries across the UK. The Commissions are required to report on their reviews to the Speaker of the House of Commons.

By-Elections

When a parliamentary seat becomes vacant between general elections (due to death, resignation, or disqualification), a by-election is held to fill the vacancy. By-elections are conducted under the same FPTP system as general elections. They are governed by the Representation of the People Acts and administered by the relevant Local Returning Officer. By-elections have historically been occasions for voters to send signals to the government, often resulting in significant swings against the governing party. The procedure for vacating a seat was reformed by the House of Commons Disqualification Act 1975 and the procedure for resignation remains governed by the archaic Chiltern Hundreds mechanism, under which an MP applies for a nominal office of profit under the Crown to disqualify themselves from membership. By-elections are also used to fill vacancies in the devolved legislatures.

The Electoral Commission

The Electoral Commission was established by the Political Parties, Elections and Referendums Act 2000 (PPERA) as an independent body responsible for overseeing elections and regulating political finance. Its functions include maintaining the registers of political parties, regulating party donations and expenditure, setting standards for electoral administration, conducting electoral research, and promoting public participation in elections. The Commission also reviews boundary arrangements, defines constituency boundaries for the devolved legislatures, and reports on the conduct of elections and referendums. It is accountable to the Speaker’s Committee on the Electoral Commission, a parliamentary body, and is funded directly by Parliament. The Commission played a central role in the EU referendum (2016), overseeing the conduct of the campaign and the regulation of spending. Following concerns about electoral fraud and foreign interference, the Commission’s powers were strengthened by the Elections Act 2022, which introduced voter identification requirements, reformed postal voting, and enhanced the Commission’s enforcement powers.

Conclusion

The UK’s electoral systems reflect a compromise between different constitutional values: the stability and accountability associated with FPTP, and the fairness and representativeness associated with proportional systems. The coexistence of multiple electoral systems for different levels of government creates complexity but allows each to be tailored to the specific constitutional context. The Electoral Commission provides independent oversight and regulation, maintaining public confidence in the integrity of the electoral process. Ongoing debates about electoral reform—including proposals to adopt a proportional system for the House of Commons—continue to shape the constitutional landscape, though no major reform has been implemented at Westminster level since the introduction of the single transferable vote for Northern Ireland elections.