General Elections

The chart below provides data on share of votes by party in UK General Elections from 1918 to 2019. This chart and supporting reference table and notes are available in the Briefing Paper on page 7. Results for each individual UK constituency at every General Election from 1918 to 2019 may be found in a further Library data download on General Election Results.

vote share at general elections


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. In 2019, the Party won 365 seats. This was the most they have held since 1987.


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. 

In 2019, Labour won 202 seats, their lowest number since 1935. 

Liberal Democrats

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 had defected from Labour.

The Alliance received a quarter of votes in the 1983 election but won just 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 2010, there were 57 Liberal Democrat MPs, but their number fell to 8 in 2015.  In 2017 the number of Liberal Democrat MPs rose to 12, before decreasing to 11 in 2019.

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 SNP’s best performance.

In 2019, the SNP won 48 seats and 45% Scottish vote share. This was 8 percentage points up on 2017, although it did not return to its previous height of 50% in 2015.

Plaid Cymru

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, 2017 and 2019. 

Green Party

The Green Party won a House of Commons seat for the first time at the 2010 General Election, this seat (Brighton Pavilion) remained the only Green seat after the 2015, 2017 and 2019 General Elections. In 2019, the party increased its vote share compared to 2017, but did not equal the record 3.8% vote share won at the 2015 General Election. 

Ulster Unionists

Since the Northern Ireland House of Commons (Stormont) was established in 1921, the Ulster Unionists dominated elections to Westminster as well as to the devolved Northern Ireland Parliament. The Ulster Unionists took the Conservative whip at Westminster until 1972. In this paper, Ulster Unionist general election candidates are listed as Conservatives for elections up to 1970 but are listed separately from 1974.

Democratic Unionist Party

The Democratic Unionist Party (DUP) has replaced the Ulster Unionist as the main Northern Ireland unionist party in 2001. In 2019, the DUP won eight seats, two fewer than in 2017. Unionists now have fewer Westminster seats than Nationalists for the first time since Northern Ireland’s establishment in 1922.

Sinn Féin

Sinn Féin won seven seats at the 2019 General Election, the same as in 2017. This is its highest number since the establishment of Northern Ireland in 1922. The Party maintained its number of seats despite 7 percentage points lower vote share in 2019 compared to 2017.

Social Democratic and Labour Party

The Social Democratic and Labour Party (SDLP) gained two seats in 2019. This was a recovery from failing to win any seats in the House of Commons in 2017, for the first time since its formation in 1970. 

Characteristics of MPs

Men and Women

220 women MPs were elected at the 2019 General Election (34% of all MPs). In total, 552 women have been elected to the House of Commons since 1918.

Section 2.6 (p. 34) in the Briefing Paper includes a table which shows women MPs elected at general elections by party 1918-2019.


As individual’s ethnicity is self-defined, it is hard to obtain historical records of MPs’ ethnicity. It is generally said that the first MPs from minority ethnic backgrounds since World War II were elected in 1987, when four Labour MPs were from minority ethnic backgrounds.

Table 8 (p. 37) in the Briefing Paper shows MPs from minority ethnic backgrounds elected at general elections, 1987-2019.

Other characteristics of MPs

Briefing Paper includes information on the following:

House of Commons by-elections

Great Britain

Generally parties in government perform poorly at by-elections while opposition parties make gains. There have been sixteen by-elections since the new Parliament was elected in December 2019 (as of 9 August 2023).

Table 12 (p. 47) in the Briefing Paper shows a summary of parliamentary by-elections in Great Britain, 1945 to date.

Northern Ireland

There were by-elections in Northern Ireland in seven of the last nineteen Parliaments (detailed statistics are available in the Table 14a and 14b (pp. 62-64 in the Briefing Paper), including one in the last parliament.

Devolved legislatures and London elections

Senedd Cymru

Since the establishment of the National Assembly for Wales in 1999 Labour has had the largest share of Assembly seats. In 2021 Labour won 30 seats. The Conservatives made the largest gains and replaced Plaid Cymru as the second largest party. UKIP failed to hold onto most of its 2016 gains.

Table 16 (p. 70) in the Briefing Paper shows National Assembly for Wales elections, 1999-2021.

Scottish Parliament

The Scottish National Party has dominated the Scottish Parliament since 2007 when it overtook the Labour Party by one seat. The Conservatives became the second largest party after overtaking Labour by seven seats in 2016. In 2021, the SNP won the most seats with 44.2% of the vote but failed to win an overall majority.

Table 17 (p. 72) in the Briefing Paper shows Scottish Parliament elections, 1999-2021.

Northern Ireland Assembly

With the election of 27 Sinn Féin MLAs, a nationalist party became the largest party in the Assembly for the first time following the 2022 Northern Ireland Assembly elections. As of December 2022, no Executive has been formed and new elections are expected.

Table 18 (p. 74) in the Briefing Paper shows Northern Ireland Assembly elections: 1998-2022.

London Assembly

In the five elections held since the establishment of the Assembly in 2000, only Conservative and Labour Members have been elected on the constituency ballot, with other parties picking up seats from the London-wide list. Labour became the largest party after winning 12 seats in the 2012 election and maintained its share in 2016 but lost one London-wide seat to the Conservative party in 2021.

Table 20a (p. 76) in the Briefing Paper shows London Assembly seats by party, 2000-2021.

Local Elections

Council Elections

The chart below provides data on party affiliation of councillors in the period from 1973 to 2023. This chart and supporting reference table is available in the Briefing Paper section 6, pp 82-84.

party affiliation of local councillors

Mayoral elections

Elections for the Mayor of London have been held every four years since 2000, using the Supplementary Vote system. In 2021 Labour’s Sadiq Khan was re-elected Mayor of London.

Table 21 (p. 78) in the Briefing Paper shows London Mayoral Elections, 2000-2021.

Elected mayors currently hold office in 16 local authorities (excluding Greater London). 

The first election for elected mayors of combined authorities (known as “Metro-mayors”) took place in 2017. In 2022, seven of the nine elected combined authority mayors are Labour and two are Conservative. Tables 27-28 (pp. 90-92) in the Briefing Paper show data for Mayoral Elections, 2000-2022. Detailed results are available in the data download file on this page. 

Additional data

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