Our new database, published today (19 August) compares the electoral performance of major parties in every constituency and region of the UK, at each of the 27 general elections since 1918.

Beginning with the first election held after the Representation of the People Act 1918, which allowed all men aged over 21 and some women over 30 to vote, the data allows users to trace the decline of the Liberals and the rise of Labour, the strength of the Conservative and Labour Parties in the post-war period, the re-birth of multiparty politics from the 1970s, and the growing political divergence between the nations and regions of the UK.

We hope to add further detail to the data, such as the gender of candidates and maps of results, in the coming months.

To mark its launch, we’ve pulled out some key facts from the data. Want to know which winning candidate had the greatest number of votes? The closest four-way contests? Or the smallest majorities? Then read on…

The largest and smallest electorates

The largest ever electorate since 1918 was recorded in Essex Romford, where 167,939 were registered at the time of the 1935 General Election. The five smallest recorded electorates (excluding those of university seats) were all in London in 1945, presumably being the result of war damage and depopulation, with the City of London having 10,851 voters.

In the 2017 General Election, the largest electorate was the Isle of Wight, with around 110,000 voters, and the smallest was 21,000 in Na h-Eileanan An Iar (Western Isles).

Prior to 1918, one House of Commons constituency with a strong claim to have the fewest number of electors was Old Sarum in Wiltshire, which had two MPs and three voters in 1728. But due to the lack of electoral registers for the period, we can’t be certain it was the smallest ever.

A chart showing that London, Essex and Northern Ireland constituencies have had the largest electorates since 1918. The five smallest were all in London.

The highest and lowest turnouts

Since 1918, turnout in UK general elections has averaged 73%. Due to the low turnout amongst the armed forces and the large number of uncontested seats, the lowest turnout since WWI was the election of 1918. In recent years, the lowest turnout was in 2001 (59%).

In terms of constituency-level turnouts, the five highest turnouts since 1918 have all been in two constituencies: Fermanagh and South Tyrone, and Lancashire Darwen.

The five lowest constituency turnouts were all seen in the 1918 General Election. The lowest turnout in recent years was Liverpool Riverside in 2001, at 34%.

A chart showing the highest turnouts were in Northern Ireland and Lancashire. The lowest were in London and the West midlands in 1918.

Highest and lowest shares of the vote for major parties in Great Britain

The top five vote shares were all achieved before 1945, while the five lowest occurred in 2015 and 2017.

The highest Liberal/Liberal Democrat vote share was recorded in Caernarvon District in 1924, with 82.5% of the vote. The Liberals did not stand candidates in many constituencies during the lowest-point of the party’s fortunes in the 1940s and 1950s. If they had, poorer performances could have been registered than those in 2015 and 2017.

The lowest Conservative vote share recorded in Great Britain was seen in Glamorganshire Pontypridd in 1918, where the party received 1.1% of the vote. Labour recorded its worst general election vote constituency vote share in Glasgow Bridgeton in 1935, receiving 2.2% of the vote.

The highest SNP vote share at a general election was recorded in the Western Isles in the February 1974 General Election, at 67%.

Plaid Cymru received its highest vote share at Caernarfon in 1992 (59%).

A chart showing that before 1945, Conservative and Labour dominated the top major party vote shares. The Liberal Democrats in 2015 and 2017 hold the record for the lowest.

Largest and smallest majorities since 1918

The largest majorities by percentage of votes in the UK have tended to occur in Northern Ireland. In both 1955 and 1959, the Ulster Unionist candidate George Currie was only opposed by Sinn Féin in Down North, resulting in his 96% majority in 1959 and one of 94% in 1955.

Between the traditional three major GB parties, the largest majorities occurred in 1918 and 1945. In the 2017 General Election, Liverpool Walton had a Labour majority of 77% over the Conservatives (86% to 9%), and in Knowsley the Labour majority was 76% (85% to 9% Conservatives).

A chart showing the five top majorities by percentage of the vote in Great Britain since 1918. West Ham Plaistow received 89.7% in 1918.
A chart showing the five largest majorities in Great Britain, by number of votes. In 1931 Bright received a majority of 62.25 thousand.

The largest majorities by number of votes in Great Britain coincided with the strongest electoral showings of the Conservative Party under the National Coalition Government in 1931 and 1935, when the party won more than 50% of the vote in both elections. The largest Labour majority was recorded in Knowsley in 2017, gaining more than 47,000 votes and 85% of the vote. 

The smallest majorities, in contrast, occurred when the party system was in relative flux, being associated with the stronger performances of parties other than Labour and the Conservatives.

Smallest majorities in UK general elections since 1918
WinnerSecondVote marginElection
Derbyshire IlkestonNational LabourLabour21931
North East FifeSNPLiberal Democrat22017
Winchester*Liberal DemocratConservative21997
Leeds WestLabourConservative31924
CarmarthenLabourPlaid Cymru3Feb 1974

*The result was voided in the High court shortly after

Closest three and four-way contests

The closest three-way result was in Caithness and Sutherland in 1945, where 0.37% of the vote separated the first and third-placed candidate. The sitting MP and Liberal Leader, Archibald Sinclair, fell from first to third place, but remained only 61 votes behind the Unionist/Conservative winner. He stood again in 1950, moving to second place in another close contest, losing to the Conservative candidate by 1.4% of the vote.

Recent close three-way contests have not included the ‘traditional’ trio of Conservative, Labour and Liberal Democrat. The close contest in Lanark and Hamilton East in 2017 was between the SNP, Labour and Conservatives. In 2015 less than 1.25% of the vote separated the Conservatives, Labour and UKIP in Thurrock.

Recent four-way marginals reflect the growth of the Greens, SNP and Plaid Cymru.

Closest three-way marginals since 1918
ElectionConstituencyWinner% gap 1st
3rd place
Winning %
1945Caithness and SutherlandConservative0.37%33.5%
2017Lanark and Hamilton EastSNP0.71%32.6%
1929Breconshire and RadnorshireLabour0.76%33.7%
Oct 1974East DunbartonshireSNP0.86%31.2%
1929Gloucestershire ThornburyConservative1.14%34.0%
Closest four-way marginals since 1918
ElectionConstituencyWinner% gap 1st
4th place
Winning %
1992Inverness Nairn and LochaberLib Dem3.42%26.05%
1922Portsmouth CentralConservative5.39%26.82%
2001Argyll and ButeLib Dem9.08%29.86%
2010Norwich SouthLib Dem10.35%29.36%
2017CeredigionPlaid Cymru10.85%29.20%

Further reading

Note: This Insight was updated on 20 August 2019 to include more detail on how the five smallest electorates were identified.

About the author: Philip Loft is a research at the House of Commons Library, specialising in social and general statistics.

Image: Polling Stations, general Election 2015 / Andy Thornley / CC BY 2.0