Political party affiliation in the United Kingdom

Labour Party

In the Labour Party's 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.^[28]

In 2025, the Labour Party's membership was recorded as 264,754.^[29]

Conservative Party

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

Liberal Democrats

The Liberal Democrats membership increased sharply after the confirmation on 18 April 2017 of the 8 June 2017 general election.^[30] Membership again increased sharply in the period before and after the two elections of May 2019, for the UK Councils and the European Parliament, though it fell again after the general election that year.

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.^[3] Membership peaked at over 125,000 in August 2018,^[31] before falling by tens of thousands in the final years of Nicola Sturgeon's leadership.^[32]

Reform UK

Membership increased by over 50% from 31,000 to 45,000+ in the eight days after Nigel Farage announced he would be returning to lead the party.^[33]

Restore Britain

Restore Britain experienced rapid membership growth following its launch as a political party on 13 February 2026. On 16 February 2026, the party announced that it had reached 50,000 members just days after its formation.^[34] Two days later, party leader Rupert Lowe said that membership had risen to 70,000.^[35] The party subsequently surpassed 96,000 members by 3 June 2026.^[36] On 16 June 2026, The Times reported that Restore Britain had 130,000 paying members.^[7]

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 up to that date.^[37] On 19 September 2025, it was revealed that the party had reached over 75,000 members.^[38] Less than a month later, on 9 October 2025, the party tweeted it had reached 95,000 members,^[8] a day after announcing it had surpassed 90,000.^[39] This "surge" has been accredited to their new leader, Zack Polanski, who was elected a month prior.^[40] On 12 October 2025, the party reached a record-breaking 100,000 members, marking an over 45% increase since Polanski was elected,^[41] and as of 13 April 2026, the Green Party has over 226,000 members.^[29][42]

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).

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.^[43] 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".^[44] Veteran Labour MP Barry Sheerman also joined calls for the election to be "paused" over the fears of infiltration by other parties.^[45] 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.^[46] Harriet Harman at the time admitted that as many as 100,000 people may be blocked from voting.^[47]

The number of those rejected eventually reached 56,000,^[48] around 9.1 per cent of the 610,753 considered eligible to vote at the start of the contest.^[49] According to the party, 45,000 of those were rejected for not being on the electoral register.^[50] 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.^[51] A number of high-profile individuals have been blocked from voting, including Marcus Chown,^[52] Jeremy Hardy, Douglas Henshall,^[53] Ken Loach,^[52] Francesca Martinez,^[53] Mark Serwotka,^[54] Pete Sinclair,^[55] Mark Steel,^[56] Luke Wright^[57] and Toby Young.

Andrew MacKinlay, a former Labour MP, further alleged that Labour was attempting to rig its own leadership election against Corbyn;^[58] a view shared by Jeremy Hardy.^[59] Such allegations became known to the media – and particularly Corbyn supporters – as the "Labour Purge", with #LabourPurge trending on Twitter.^[58] Claims of such a "purge" of Corbyn supporters were rejected by Harman who insisted that the exclusion processes were impartial to candidates.^[60] Scottish newspaper The National printed a page-long satirical cartoon speculating further vote-rigging by Labour's leadership.^[61]

Brexit

Conservative peer Michael Heseltine had the whip removed in 2019 after expressing his intention to vote Liberal Democrat.^[62] Conservative policy appears to make such expulsions discretionary,^[63] despite threats from Conservative Campaign Headquarters.^[64] Tony Blair's support for pro-remain parties led to questions about why he had not been expelled from the Labour Party.^[65] Alastair Campbell was expelled from the Labour Party after saying he voted for the Liberal Democrats in the 2019 European election.^[66] Many Labour members came out in support of Campbell using the hashtag #expelmetoo, reporting that they had similarly voted for the Liberal Democrats or other remain parties.^[67]