There has been a large decrease in reported membership of UK political parties over the post-war period. In 2010, only 1.0% of the electorate was a member of one of the three main political parties. Labour had approximately 194,000 members, the Conservatives 177,000 and the Liberal Democrats 65,000. However in the early 1950s, the Conservatives claimed nearly 3 million members while Labour claimed more than 1 million members.
Commons Library Standard Note SN05125 sets out available data on membership of the three main parties back to 1928, as well as more recent figures for smaller parties. It also looks at membership of other organisations, including trade unions and pressure groups, and the decline in party membership in other European countries.