As the Party Membership Project has suggested: “[p]arty membership is vital for the health of our representative democracy. Members contribute significantly to the election campaigns and to party finances. They are people who pick party leaders.” What do we know about party membership, and how significant are the figures as a proportion of the electorate?

Latest data on party membership

The latest available estimates from political parties’ head offices, press releases and media reports indicate that:

Chart showing the membership of UK political parties

Analysing party membership

Comparing 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. Nonetheless, the majority of main parties voluntarily include membership figures in annual accounts for the year ending 31 December, submitted to the Electoral Commission.

Although all parties are required to submit these annual accounts by the Political Parties, Elections and Referendums Act (2000), they’re not obliged to include membership data. 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. This data is presented in a graph above.


Membership as proportion of electorate

Membership of the Conservative, Labour and the Liberal Democrat parties has increased to around 1.6% of the electorate in 2018, compared to a historic low of 0.8% in 2013. Across the UK, the Labour Party’s membership increased from 0.4% in 2013 to 1.2% in 2018.

In April 2018, SNP membership was around 118,000, compared to 25,000 in December 2013; assuming all Scottish National Party members are in Scotland, SNP membership increased across Scotland from 0.6% of the electorate in 2013 to 3.0% in 2017 and 2018. In April 2018, membership of the Green Party (England and Wales) was around 41,100, compared to 13,800 in December 2013. UKIP’s membership increased from 32,000 in December 2013 to around 42,200 in December 2014, though has since fallen to around 21,200 in April 2018.

Chart showing membership of the electorate

Data published in annual accounts

Political parties are under no legal obligation to publish membership statistics. Many parties provide party membership figures for the year ending 31 December in annual accounts submitted to the Electoral Commission. The latest estimates released by the Electoral Commission are shown in the graph below. More information is available in the House of Commons Library Briefing paper – Membership of UK Political Parties.

 Membership of UK political parties (thousands)

For more information read our new paper, Membership of UK political parties.

Image credit: A delegate voting on a motion at Liberal Democrat Conference; by NCVO London. Creative Commons License 2.0