The Electoral Commission's Register of Political Parties lists the details of political parties registered to contest elections in the United Kingdom, including their registered name. Under current electoral law, including the Registration of Political Parties Act 1998, the Electoral Administration Act 2006, and the Political Parties, Elections and Referendums Act 2000, only registered party names can be used on ballot papers by those wishing to contest elections. Candidates who do not belong to a registered party can use "independent" or no label at all. , the Electoral Commission showed the number of registered political parties in Great Britain and Northern Ireland as 410.

Before the middle of the 19th century, politics in the United Kingdom was dominated by the Whigs and the Tories. These were not political parties in the modern sense but somewhat loose alliances of interests and individuals. The Whigs included many of the leading aristocratic dynasties committed to the Protestant succession, and later drew support from elements of the emerging industrial interests and wealthy merchants, while the Tories were associated with the landed gentry, the Church of England and the Church of Scotland.

By the mid 19th century, the Tories had evolved into the Conservative Party, and the Whigs had evolved into the Liberal Party. The concept of right and left came originally from France, where the supporters of a monarchy (constitutional or absolute) sat on the right wing of the National Assembly, and republicans on the left. In the late 19th century, the Liberal Party began to lean towards the left. Liberal Unionists split off from the Liberals over Irish Home Rule and moved closer to the Conservatives over time.

The Liberals and Conservatives dominated the political scene until the 1920s, when the Liberal Party declined in popularity and suffered a long stream of resignations. It was replaced as the main anti-Tory opposition party by the newly emerging Labour Party, which represented an alliance between the labour movement, organised trades unions and various socialist societies.

Since then, the Conservative and Labour parties have dominated British politics, and have alternated in government ever since. However, the UK is not a two-party system as other parties have significant support. The Liberal Democrats were the third largest party until the 2015 general election when they were overtaken by the Scottish National Party in terms of seats and UK political party membership, and by the UK Independence Party (UKIP) in terms of votes. The Liberal Democrats regained the status of the third largest political party in the UK by seats with the outcome of the 2024 United Kingdom general election.

The UK's first-past-the-post electoral system leaves small parties disadvantaged on a UK-wide scale. It can, however, allow parties with concentrations of supporters in the constituent countries to flourish. In the 2015 election, there was widespread controversy when the UK Independence Party (UKIP) and the Green Party of England and Wales received 4.9 million votes (12.6% of the total vote for UKIP and 3.8% for the Greens) yet only gained one seat each in the House of Commons. After that election, UKIP, the Liberal Democrats, the Scottish National Party, Plaid Cymru, the Green Party of England and Wales, together with the Scottish Greens and the Green Party Northern Ireland, delivered a petition signed by 477,000 people to Downing Street demanding electoral reform.

Since 1997, proportional representation-based voting systems have been adopted for elections to the Scottish Parliament, the Senedd (Welsh Parliament), the Northern Ireland Assembly, the London Assembly and (until Brexit in 2020) the UK's seats in the European Parliament. In these bodies, other parties have had success.

Traditionally political parties have been private organisations with no official recognition by the state. The Registration of Political Parties Act 1998 changed that by creating a register of parties.

Membership of political parties has been in decline in the UK since the 1950s. Membership has fallen by over 65% since 1983, from 4% of the electorate to 1.3% in 2005.

Parties with representation in the House of Commons

Party Founded Politicalposition Ideology Leader House ofCommons House ofLords ScottishParliament Senedd NIAssembly LondonAssembly Localgovernment Labour Party 1900 Centre-left Andy Burnham Conservative and Unionist Party 18341912 Kemi Badenoch Liberal Democrats 1988 Centre tocentre-left Ed Davey Scottish National Party (SNP) 1934 Centre-left John Swinney Reform UK 2018 Right-wing to far-right Nigel Farage Sinn Féin 1970 Centre-leftto left-wing Michelle O'Neill Democratic Unionist Party (DUP) 1971 Right-wing Gavin Robinson Green Party of England and Wales 1990 Left-wing Zack Polanski Plaid Cymru 1925 Centre-left Rhun ap Iorwerth Social Democratic and Labour Party (SDLP) 1970 Centre-left Your Party 2025 Left-wing Collective leadership Alliance Party of Northern Ireland 1970 Centre tocentre-left Naomi Long Ulster Unionist Party (UUP) 1905 Centre-right Jon Burrows Traditional Unionist Voice (TUV) 2007 Right-wing Jim Allister Restore Britain 2026 Far-right Ethnic nationalism Rupert Lowe

Parties with representation in UK constituent country legislatures There are a few political parties in the United Kingdom that do not have representation in the House of Commons, but have elected representatives in the Northern Ireland Assembly and Scottish Parliament. These are: Party Founded Political position Ideology Current leader ScottishParliament NI Assembly Localgovernment 1990 Centre-leftto left-wing Ross Greer,Gillian Mackay (PBP) 2005 Richard Boyd Barrett

Party descriptions PartyDescriptionLabour PartyA social democratic party that has its roots in the trade union movement. The party has several internal factions, which include: Progress, which promotes a continuation of New Labour policies and is considered to be on the right of the party; the soft-left Open Labour; Momentum, which represents the party's left-wing, democratic socialist grouping; and Blue Labour, which promotes socially and culturally conservative values while remaining committed to labour rights and left-wing economics. Labour also has candidates who stand on a split-ticket with the Co-operative Party.Co-operative PartyA party that promotes cooperative principles and values, providing political representation for the British co-operative movement. Since 1927, the party has been in an electoral alliance with the Labour Party, standing joint candidates under the Labour and Co-operative label.Conservative and Unionist PartyA politically conservative party loosely divided into three categories: the One Nation Conservatives, the Thatcherites, who strongly support a free market with restrained government spending and tend to be Eurosceptic; and the Cornerstone Group.Liberal DemocratsA liberal party; its main branches are social liberals based around the Social Liberal Forum, and the more centrist Liberal Reform grouping, which places more of an emphasis on economic liberalism. There is also a social democratic faction and influence within the party.Scottish National Party (SNP)Scottish nationalist and social democratic party which supports Scottish independence and membership of the European Union or further devolution for Scotland.Irish republican party dedicated to the reunification of Ireland and the creation of a new republic based on democratic socialist values. It holds a policy of abstentionism for the House of Commons, with its MPs not taking their seats in this legislature.Reform UKRight-wing populist and hard Eurosceptic party.Democratic Unionist Party (DUP)Strongly British unionist party in Northern Ireland which promotes social and national conservatism.Green Party of England and WalesGreen party that combines environmentalism and sustainability with left-wing economic policy, while taking a progressive approach on social issues. The party also has eco-socialist and anti-capitalist factions, such as the Green Left grouping.Centre-left, social democratic, and Welsh nationalist party in favour of Welsh independence or further devolution of powers to Wales while Wales remains part of the UK. (SDLP)Irish nationalist and social-democratic party supporting a united Ireland.Alliance Party of Northern Ireland (APNI)Liberal, nonsectarian and pro-European political party in Northern Ireland.Ulster Unionist Party (UUP)Conservative and Unionist party in Northern Ireland, taking a somewhat "softer" stance on social issues than the DUP. The party was formerly tied to the Conservative Party in Great Britain.Traditional Unionist Voice (TUV)Strongly social and national conservative unionist party in Northern Ireland. It has formed an alliance with Reform UK.Scottish GreensGreen party in favour of Scottish independence and Scottish republicanism.People Before Profit (PBP)Socialist and Trotskyist party that is active in both the Republic of Ireland and Northern Ireland.Your PartyA socialist party.Restore BritainA far-right party advocating for mass deportations of illegal immigrants.

Parties with representation only in UK local government

Great Britain-wide or UK-wide parties PartyFoundedPolitical positionIdeologyLeaderLocal authorities Councillors Liberal Party 1989 Centre Liberalism (British), Euroscepticism Steve Radford Liverpool, North Yorkshire, East Devon, Wyre Forest 7Workers Party of Britain2019Left-wing to far-leftSocialism, social conservatism, EuroscepticismGeorge Galloway Rochdale, Calderdale, Bury, Birmingham 7 Social Democratic Party (SDP) 1990 Social democracy, cultural conservatism, communitarianism, Euroscepticism William Clouston Leeds, Wakefield, Durham 5Party of Women 2024 Single-issue Gender-critical feminism, anti-transgender Kellie-Jay Keen-Minshull Maldon 1 Trade Unionist and Socialist Coalition (TUSC) 2010 Left-wing to far-left Trade unionism, socialism Dave Nellist Wrexham County Borough Council 1

Parties that only stand in a country or region of the UK PartyFoundedAreas activePolitical positionIdeologyLeaderLocal authorities Councillors Green Party Northern Ireland 1981 Northern Ireland Centre-left Mal O'Hara Ards and North Down, Belfast 5 1951 Cornwall Centre-left Cornish nationalism, civic nationalism, regionalism, social democracy, environmentalism Dick Cole Cornwall3 British Unionist Party 2015 Scotland Syncretic British unionism, Scottish unionism, Social conservatism, Social democracy, British nationalism John Ferguson North Lanarkshire Council 1 2018 Wales Centre-right Welsh nationalism, Welsh independence Gwyn Wigley Evans Ceredigion County Council 1National Flood Prevention Party 2011 England Single-issue Ewan Larcombe Windsor and Maidenhead Borough Council 1 Progressive Unionist Party (PUP) 1979 Northern Ireland Centre-left to left-wing British unionism, democratic socialism, social democracy Russell WattonCauseway Coast and Glens 1 Propel 2020 Wales Welsh nationalism, Welsh independence, localism, sovereignism Neil McEvoy Cardiff 1

Local parties