Voting systems in the UK

Until 1997 nearly all elections in the UK used the first-past-the-post (FPTP) voting system. The exceptions were local and devolved elections in Northern Ireland which used the single transferable vote (STV) system from the 1970s. University seats in the House of Commons also used STV from 1918 until their abolition in 1950.

Since 1997 several different voting systems have been introduced for different elections across the country.

The briefing also highlights recent developments in the UK. These include the decision by the Senedd Cymru to allow local councils to choose whether they are elected by FPTP or STV; proposals for the Senedd Cymru to adopt a new type of proportional electoral system for the next Senedd elections in 2026, and the abolition of the supplementary vote system for mayoral and police and crime commissioner elections. From May 2023 these elections will use FPTP.

Current voting systems

The current coting systems in use are summarised below.

First Past the Post

FPTP is the current system for electing MPs to the House of Commons. The UK is divided into 650 separate constituencies, each of which elects a single Member of Parliament.

Winning candidates must receive more votes than any other candidate to be elected. They do not need an absolute majority of all votes cast (over 50%). 

FPTP is also used for local elections in England and Wales. In wards where two or three councillors are elected at the same time, the candidates that finish in the top two (or three as appropriate) are elected.

Additional Member System

Voters have two ballot papers on polling day. One is used to elect a constituency member using FPTP.

The second is used to vote for a party. Parties are listed on a ballot paper and the voter places a cross next to the preferred political party. Several constituencies are grouped together to form a single region and a set number of people will be elected from that region’s list. Voters in each region will vote on the same regional list.

The votes for each part of the elections are counted separately.

The FPTP seats are counted first. Once the winner in each seat has been declared the votes in the regional list election can be counted.

The share of the vote in the regional list ballot is then used to allocate regional list seats. In calculating how many list seats a party is entitled to, FPTP constiteuncy seats already won are taken into account. This helps make the result more proportional.

Single Transferable Vote (STV)

STV is a preferential voting system and operates in multi-member constituencies. Voters rank candidates in order of preference by marking 1, 2, 3 etc against the candidates’ names on the ballot paper. Voters can rank candidates within parties or across different parties.

Candidates must obtain a certain quota of votes in order to be elected. If they exceed the quota their suplus votes are reallocated. If no candidate reaches the quota, the lowest candidate is eliminated and their votes are reallocated based on second, third, and so on preferences. This process continues until all seats have been filled.

Alternative Vote (AV)

AV is also a preferential voting system. Under the AV system, voters are entitled to rank candidates in their order of preference, marking 1, 2, 3 etc against the candidates’ names on the ballot paper. In an AV election only one candidate wins but must poll over 50% of the vote.

If a candidate fails to gain 50% of the vote on the first count, the lowest candidate is eliminated and their second preferences are reallocated. This reallocation of the bottom candidate’s votes – based on second, third and fourth preferences etc – continues until one candidate gains more than 50%.