UK political party performance since 1945
The Conservative’s best result in terms of seats won since 1945 was at the 1983 General Election, when 397 MPs were elected. Its highest share of the vote was 49.7% in 1955.
At the 1997 General Election, there were 165 Conservative MPs elected and the party received 30.7% of the vote. This was its worst performance in terms of share of the vote and seats won since 1918.
The first Labour majority government was elected in 1945.
The highest share of the vote received by Labour in a general election was 48.8% in 1951, when the Conservatives won the most seats despite polling fewer votes. Labour’s worst general election performance of the post-war years was in 1983, with 27.6% of the vote and 209 seats.
In 1997, Labour’s 418 seats were the highest ever number for a single party.
The Liberal Party contested the 1983 and 1987 elections in alliance with the Social Democratic Party (SDP), before the two parties merged in 1988 to form the Liberal Democrat Party. The SDP had been established in January 1981 and by March 1982 it had 29 MPs, most of whom had defected from Labour.
The Alliance received a quarter of votes cast in the 1983 election, but won only 23 seats.
62 Liberal Democrat MPs were elected in 2005, the highest number for the Party and its predecessors since 1923 (when the Liberals won 158 seats).In 2017 the number of Liberal Democrat MPs rose to 12 from 8 in 2015. This was 45 MPs fewer compared with 57 at the 2010 General Election.
Scottish National Party
The Scottish National Party (SNP) won its first seat at a general election in 1970. The May 2015 election, when the party received 50% of the vote in Scotland and won 56 seats, was the SNPs greatest victory. In 2017, the SNP won 35 of Scotland’s 59 seats with 36.9% of the Scottish vote, a decrease of over 13 percentage points compared to 2015.
Plaid Cymru won its first seats in a general election in February 1974. The most seats won by Plaid Cymru at a general election is four, in 1992, 1997, 2001 and 2017.
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In 2017, the UK Independence Party (UKIP) lost its only seat that the party won in 2015. UKIP’s vote share declined from 12.6% to 1.8%. This was their lowest vote share since 2001. In 2017, UKIP did not finish second in any constituency, down from 120 second places in 2015.
The Green Party won a House of Commons seat for the first time at a 2010 General Election, this seat (Brighton Pavilion) remained the only Green seat after the 2015 and 2017 General Elections. In 2017, the party lost more than half its vote share compared with the 2015 election.
Source: Research Briefings – UK Parliament