The Labour Party was founded on 27 February 1900 in London. The party is described as belonging to the centre-left, and grew out of the trade union movement with which it is still linked. From 1922 onwards the Labour Party has either formed the governing party or the official opposition in the UK parliament. In January 1924 Ramsay MacDonald became the first Labour Prime Minister. Other Labour prime ministers include Clement Atlee, Harold Wilson, James Callaghan, Tony Blair and Gordon Brown.

During the Second World War the Labour Party formed part of a wartime coalition government. The party won the 1945 UK general election and in 1948, went on to establish the National Health Service (NHS).