# Political party affiliation in the United Kingdom

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Membership and supporter status within political parties in the United Kingdom typically contain restrictions including:
* Age restrictions
* Citizenship restrictions
* A commitment to the party's principles
* Limiting holding membership of other political parties
* Limiting standing against officially endorsed candidates
* Membership of specifically prohibited political parties
* Personal conduct expectations and party rule compliance
Practically, involvement in a political party without membership may limit an individual's involvement. Parties that offer a lower level of affiliation, such as supporter status tend to have looser constraints.

## History

Membership of political parties has been in decline in the UK since the 1950s, falling by over 65% from 1983 (4 per cent of the electorate) to 2005 (1.3 per cent). In 2022, 1.5% of the British electorate were members of the Conservative Party, Labour Party, or the Liberal Democrats. Typically party affiliation allows an individual to support only a single party. However, notable exceptions to this are: the Co-operative Party which permits its members to also have membership of the Labour Party and the Social Democratic and Labour Party (SDLP); and the Women's Equality Party which allows its members to also have membership of any other political party.
According to the UK Parliament website sourced from a report by Olympic Britain, during the 1950s there were 2.8 million members of the Conservative Party and 1 million Labour Party members. In the years after 1945 until the early 1990s, supporters of the Socialist and Cooperative parties and trade unions linked with the Labour Party increased the overall Labour Party movement by 5 to 6 million, from which point they began to fall and currently number about 3.5 million.
Despite being founded in 1900, the Labour Party did not begin keeping track of its membership until 1928. On the other hand, the Conservative Party rarely releases their total membership statistics; additionally, there are no clear membership statistics for the Conservative party before 1945. It is estimated that between World War 1 and World War 2, membership levels were around 1.5 million; however, exact numbers are unknown.

## Current membership

| Party | Current membership | Registered supporters | Date | Region |
| Labour | 309,000 | N/A | February 2025 | UK |
| Reform UK | 200,000+ | N/A | February 2025 | UK |
| Conservatives | 131,680 | N/A | November 2024 | UK |
| Liberal Democrats | 90,000+ | 17,102 | 29 April 2023 | UK |
| Scottish National Party (SNP) | 69,325 | N/A | December 2023 | Scotland |
| Green Party of England and Wales | 59,000+ | N/A | 16 July 2024 | England and Wales |
| Co-operative Party | 13,194 | N/A | 31 December 2022 | UK |
| Plaid Cymru | c.10,000 | N/A | 30 August 2022 | Wales |
| Scottish Greens | 7,646 | N/A | 24 April 2023 | Scotland |
| Alba Party | 7,500 | N/A | 13 May 2023 | Scotland |
| Workers Party of Britain | 7,469 | N/A | January 2025 | Great Britain |
| UK Independence Party (UKIP) | 3,888 | N/A | 31 December 2020 | UK |
| Socialist Workers Party | 2,504 | 6,000 | 2023 | Great Britain |
| English Democrats | 2,500 | N/A | 2015 | England |
| Social Democratic Party (SDP) | 2,000 | N/A | January 2021 | UK |
| Communist Party of Britain (CPB) | 1,808 | N/A | 31 December 2023 | Great Britain |
| British National Party | 500 | N/A | 2015 | UK |
| National Liberal Party | 328 | 328 | 2023 | Great Britain |
| Official Monster Raving Loony Party | 311 | N/A | 2023 | UK |
| Socialist Party of Great Britain | 300 | N/A | 2023 | Great Britain |
| Gwlad | 297 | N/A | 2022 | Wales |
| Wessex Regionalists | 21 | N/A | 2021 | England |

### Labour Party

In the 2020 leadership election 490,731 people voted, of whom 401,564 (81.8%) were full members, 76,161 (15.5%) had affiliated membership and 13,006 (2.6%) were registered supporters. The registered supporter class was abolished in 2021.

### Conservative Party

The Conservative Party's membership was revealed as 131,680 at the end of the 2024 Conservative Party leadership election.

### Liberal Democrats

Membership increased sharply after the confirmation on 18 April 2017 of the 8 June 2017 general election. Membership again increased sharply in the period before and after the two elections of May 2019, for the UK Councils and the European Parliament.

### Scottish National Party

There was a huge surge in membership after the 2014 Scottish independence referendum, prior to which the SNP had just over 25,000 members. Membership peaked at over 125,000 in August 2018. Membership numbers then fell by tens of thousands in the final years of Nicola Sturgeon's leadership.

### Reform UK

Membership doubled in the eight days after Nigel Farage announced he would be returning to lead the party.

### Green Party of England and Wales

On 31 December 2015, the Green Party of England and Wales announced its membership as 63,219, its highest known membership to date.

### Co-operative Party

Though the Co-operative Party stands joint candidates with the Labour Party, their membership bases are independent (members have the option of joining both parties).

## Enforcement

There are few high-profile cases of membership criteria enforcement and as such tend to happen under exceptional circumstances.

### 2015 Labour leadership election

During the 2015 Labour party leadership election it emerged that 260 former candidates from the Green Party, Left Unity and the Trade Union and Socialist Coalition had attempted to become registered supporters, but were subsequently blocked from voting. Shortly before this, it was revealed that Conservative MP and former junior minister Tim Loughton had been caught applying to become a registered Labour supporter, subsequently claiming that his intention was to "blow the gaff on what a complete farce the whole thing is". Veteran Labour MP Barry Sheerman also joined calls for the election to be "paused" over the fears of infiltration by other parties. The Labour Party told representatives of the four candidates at a meeting on 11 August that 1,200 members and supporters of other parties had been excluded and a further 800 were under investigation. Harriet Harman at the time admitted that as many as 100,000 people may be blocked from voting.
The number of those rejected eventually reached 56,000, around 9.1 per cent of the 610,753 considered eligible to vote at the start of the contest. According to the party, 45,000 of those were rejected for not being on the electoral register.
Labour also confirmed that it would cancel supporters' votes after they had been cast, if it was found that they were members of other parties. A number of high-profile individuals have been blocked from voting, including Marcus Chown, Jeremy Hardy, Douglas Henshall, Ken Loach, Francesca Martinez, Mark Serwotka, Pete Sinclair, Mark Steel, Luke Wright and Toby Young.
Andrew MacKinlay, a former Labour MP, further alleged that Labour was attempting to rig its own leadership election against Corbyn; a view shared by Jeremy Hardy. Such allegations became known to the media – and particularly Corbyn supporters – as the "Labour Purge", with #LabourPurge trending on Twitter. Claims of such a "purge" of Corbyn supporters were rejected by Harman who insisted that the exclusion processes were impartial to candidates. Scottish newspaper The National printed a page-long satirical cartoon speculating further vote-rigging by Labour's leadership.

### Brexit

Political realignments in the Brexit process led to Ann Widdecombe being expelled from the Conservatives after she defected to the Brexit Party in the 2019 European elections to run for MEP. Michael Heseltine has the whip removed after expressing his intention to vote Liberal Democrat. Conservative policy appears to make such expulsions discretionary. despite threats from Conservative Campaign Headquarters.
Tony Blair's support from pro-remain parties led to questions why he had not been expelled from the Labour Party. Alastair Campbell was expelled from the Labour Party after saying he voted for the Liberal Democrats in the 2019 European election. Many Labour members came out in support of Campbell using the hashtag #expelmetoo reporting they had similar voted for the Liberal Democrats or other remain parties.

## Criteria for membership

| Party | Membership restrictions |
| Conservative Party | "open to all who share its objects and values and who undertake to be bound by this Constitution" "Membership of the Conservative Party is not compatible with Membership of or association with any other registered political party" |
| Labour Party | "are not members of political parties or organisations ... declared ... ineligible for affiliation to the party." "[Must not stand in] opposition to a Labour candidate" "[Must not support] a political organisation ... who stands against an official Labour candidate" |
| Liberal Democrats | "Open to all persons who agree with its fundamental values and objectives without discrimination as to age, ethnic origin, religion, disability, gender or sexual orientation." "Membership may be revoked [due to] standing against the candidate of the Party" "Membership may be refused [due to] membership of another political party in Great Britain" |
| Democratic Unionist Party (DUP) | |
| Scottish National Party (SNP) | "I endorse the aims of the Party" "A member may not contest or be a member of any organisation [deemed to be a Political Party] contesting elections in opposition to the Party" |
| Sinn Féin | "only residents of Ireland are eligible for membership" |
| Plaid Cymru | "I endorse the aims of the Party and agree to abide by its constitution. I am not a member of any other political party active in Wales" |
| Co-operative Party | "must also be a member of a recognised co-operative" "...agree to accept the rules and to promote the policy and values of the Co-operative Party. ...not a member of any political Party other than the Labour Party or the Social Democratic and Labour Party." |
| Social Democratic and Labour Party (SDLP) | |
| Alliance Party | Disclose if you/I "am/was a member of another UK or Irish political party" and give the name of the party. |
| Green Party of England and Wales | "I/we accept the party’s aims and do not belong to any other political party." |
| Scottish Greens | "I accept and will further the aims of the Scottish Green Party, and am not a member of any other political party except a sister Green party" |
| Green Party in Northern Ireland | "not a member of any other political party." |
| Ulster Unionist Party (UUP) | |
| Traditional Unionist Voice (TUV) | Support for the principles of Unionism, Independence from the Republic of Ireland and Family values |
| UK Independence Party (UKIP) | "open to any natural person who shares the objectives and core beliefs of the Party" "[Membership shall be revoked if a member] joins another political party ... or any organisation membership of which the NEC has declared to be incompatible" "[Membership shall be revoked if a member]has set up or has aided and abetted the setting up of another political party" "[Membership shall be revoked if a member]stands against a UKIP candidate in any election" "I am not and have never been a member of Hope not Hate, Antifa, Communist League, Left Unity, Extinction Rebellion or Just Stop Oil." |
| Communist Party of Britain | "Apply to join the Communist Party by paying an initial online registration fee (£6). Once you have registered an online application you will be contacted by a representative of your local Party branch for a membership interview. New members are only admitted to the Party on acceptance by their local CP organisation. If your application to join the Communist Party is refused, you will be refunded your online registration fee, with £1 retained to cover administration costs. Please note if you apply to join and withdraw your application, your application fee is not refundable." "You must be aged 16 or above to join the Communist Party." |
| Official Monster Raving Loony Party | "One year’s membership to The Loony Party is £15". Provide a "Loony Name". |