British electoral politics has been a predominantly two party system for most of the past hundred years.
In recent decades the Conservative and Labour parties have held the vast majority of Commons seats, but a century ago most electoral contests were between the Conservatives and Liberals. The 1906 election had returned the Liberals with a 129 seat majority, but in 1955 the party claimed only six MPs.
Best of share. The chart shows the share of the vote received by parties at UK General Elections.
Labour’s chance to supplant the Liberals as the Conservatives’ main opponent came in the aftermath of WWI. Splits in the Liberal leadership meant Labour was the largest opposition party in 1918, despite winning only 57 seats. Social changes also favoured the party: the War years brought about a huge increase trade union membership, while the extension of the franchise in 1918 meant many new working class voters joined the electorate. Labour formed minority governments in 1924 and 1929 and achieved its first parliamentary majority in 1945 in a landslide election victory.
The Conservatives remained the primary political force throughout the inter-war years and the largest party in the Commons, with the exception of the 1929-31 Parliament. Labour’s rise corresponded to the supplanting of religion by class as the main social factor in determining party support, though significant numbers of working class voters evidently still backed the Conservatives. During the 1950s almost half of votes cast went to the Conservatives, from a largely working class electorate.
Together the Conservatives and Labour received around 90% of the vote in general elections between 1945 and 1970. In 2010, just 65% of the vote went to these two parties. Since 1974 the Liberals have polled around 20% of the vote, but with little reward in terms of seats.
Conservative success in the 1979 election was the first of four consecutive general election victories. The party’s vote share in these years was some six or seven percentage points lower than in the 1950s, and yet in 1983 and 1987 delivered larger majorities. Likewise Labour’s landslide win in 1997 was achieved on a 43% share, similar to what it received when it lost the 1970 election, and well below vote shares secured in the immediate post-war years. This disparity between vote share and the share of representation in the Commons is due partly to the rise of other parties, which together take lots of votes but very few seats.