On 21 August the Electoral Commission released the latest annual accounts of political parties. By combining this newly published data with estimates from political parties’ head offices, press releases and media reports we can chart party membership.

What does the latest combined data show?

Estimates from political parties’ head offices, press releases and media reports indicate that:

The Labour Party has around 540,000 members, as of April 2018, according to an unconfirmed estimate published on the LabourList. The latest official estimates, in party annual accounts, suggested more than 564,400 members, as of December 2017.

has around 540,000 members, as of April 2018, according to an unconfirmed estimate published on the LabourList. The latest official estimates, in party annual accounts, suggested more than 564,400 members, as of December 2017. The Scottish National Party has just under 125,500 members, as of August 2018.

has just under 125,500 members, as of August 2018. The Conservative Party has around 124,000 members as of March 2018.

has around 124,000 members as of March 2018. The Liberal Democrat Party has around 99,200 members, as of August 2018.

has around 99,200 members, as of August 2018. The Green Party (England and Wales) has around 39,400 members, as of August 2018.

(England and Wales) has around 39,400 members, as of August 2018. UKIP has around 23,600 members, as of August 2018.

has around 23,600 members, as of August 2018. Plaid Cymru has around 8,000 members, as of August 2018.

The latest available data shows that SNP membership has surpassed the latest reported Conservative membership figure. SNP membership rose from 118,162 in April 2018 to 125,482 in August 2018, according to information provided by the party’s headquarters. It worth noting, however, that the latest Conservative membership figure (124,000) was reported in March 2018. This therefore does not account for any possible changes since then.

Analysing party membership

Comparing party membership between political parties can sometimes be difficult. Political parties are under no legal obligation to publish membership statistics. There’s also no uniformly recognised definition of ‘membership’, nor is there an established method or body to monitor it. However, all parties are required to submit annual accounts by the Political Parties, Elections and Referendums Act (2000), and the majority of main parties voluntarily include membership figures for the year ending 31 December, which are submitted to the Electoral Commission. Therefore, when annual accounts do include these figures, they’re probably the most reliable estimates available.

An alternative source is provided on request from party head offices to the House of Commons Library, or through media reports. This data is presented in the graph above.

Data published in annual accounts

The latest estimates released by the Electoral Commission show that in December 2017:

The Labour Party had more than 564,400 members, an increase from 544,600 in December 2016.

had more than 564,400 members, an increase from 544,600 in December 2016. The Scottish National Party had around 118,200 members as of April 2018, a slight decrease from 119,000 in December 2016.

had around 118,200 members as of April 2018, a slight decrease from 119,000 in December 2016. The Liberal Democrat Party had around 97,400 members, a rise from 78,300 in December 2016.

had around 97,400 members, a rise from 78,300 in December 2016. The Green Party (England and Wales) had around 42,400 members, a decrease from 45,600 in December 2016.

(England and Wales) had around 42,400 members, a decrease from 45,600 in December 2016. UKIP had around 23,600 members, compared to more than 34,300 reported in December 2016.

had around 23,600 members, compared to more than 34,300 reported in December 2016. The Conservative Party does not publish data on party membership in annual accounts. The latest data for 2018 and 2013 was acquired from public sources and information from the Conservative Campaign Headquarters.

Further reading

Further analysis is available in the House of Commons Library Briefing paper – Membership of UK Political Parties

About the author: Lukas Audickas is an Enquiry Executive at the House of Commons Library.