The 1951 United Kingdom general election was held twenty months after the 1950 general election, which the Labour Party had won with a slim majority of just five seats. Labour called the election for 25 October 1951 hoping to increase their majority.
Attlee had decided to call the election after the King's concerns over leaving the country to go on his Commonwealth tour in 1952 with a government that had such a slim majority. The Labour government, which by now had implemented most of its 1945 manifesto, was now beginning to lose many cabinet ministers such as Ernest Bevin due to old age. The Conservatives however, due to the recent election, looked more fresh with more new MPs. As Labour began to have some policy splits during the election campaign, the Conservatives ran an efficient campaign that was well funded and orchestrated. As for the Liberals, the poor election results in 1950 only got worse.
The subsequent Labour defeat is significant for several reasons: the party polled almost a quarter of a million votes more than the Conservatives and their National Liberal allies combined, won the most votes that Labour had ever won (and has ever won as of 2014), and won the most votes of any political party in any election in British political history at the time, a record surpassed by the Conservative Party in 1992. Despite this, it was the Conservatives who formed the next government with a majority of 16. This was largely because, unlike in 1950, not every seat had a Liberal candidate, and those that did tended to be Conservative rather than Labour seats. In addition (but less significantly) under the first past the post electoral system, the Labour votes translated into increased majorities for MPs in already safe seats, rather than into gaining new seats. This was the second of three elections in the 20th Century where a party lost the popular vote but won the most seats, the others being 1929 and February 1974; it also happened in 1874.
Finally, an additional factor that almost certainly boosted the margin of Labour's victory in the popular vote was the unopposed return of four Conservative Party candidates. This was the last general election in which any candidates were returned unopposed, although there have since been unopposed by-elections.