The Conservative Party, officially the Conservative and Unionist Party, is a centre-right political party in the United Kingdom that espouses the philosophies of conservatism and British unionism. As of 2012 it is the most powerful party in the United Kingdom, being the largest single party in the House of Commons with 303 MPs, the largest party in local government with 9,391 councillors, and the largest British party in the European Parliament with 25 MEPs. It governs in coalition with the Liberal Democrats, with party leader David Cameron as Prime Minister.
Colloquially referred to as the Tory Party or the Tories, the Conservative Party was founded in 1834. The party was one of two dominant parties in the 19th century, along with the Liberal Party. It changed its name to the Conservative and Unionist Party in 1912 after merging with the Liberal Unionist Party, although that name is rarely used and it is generally referred to as simply the Conservative Party.
In the 1920s, the Liberal vote greatly diminished and the Labour Party became the Conservatives' main rivals. Conservative Prime Ministers led governments for 57 years of the 20th century, including Winston Churchill (1940–45, 1951–55) and Margaret Thatcher (1979–90). Thatcher's tenure led to wide-ranging economic liberalisation and saw the Conservatives become the most eurosceptic of the three major parties. The party was returned to government in coalition, having failed to win a majority, in 2010 under the more liberal leadership of David Cameron.
In the European Parliament, the Conservatives are the largest British party with 25 MEPs, who sit with the soft eurosceptic European Conservatives and Reformists (ECR) parliamentary group, while the party itself is a member of the Alliance of European Conservatives and Reformists (AECR) Europarty. They are the third-largest party in the Scottish Parliament and second-largest in the Welsh Assembly. They were formally allied to the Ulster Unionist Party (UUP) as part of the Ulster Conservatives and Unionists arrangement, with the UUP currently participating in the five-party Northern Ireland Executive.