Social Democratic Party (UK, 1990–present)

The Social Democratic Party (SDP) is a political party in the United Kingdom, established in 1990. The current party traces its origin to the Social Democratic Party, which was formed in 1981 by a group of dissident Labour Party Members of Parliament (MPs) and former Cabinet members Roy Jenkins, David Owen, Bill Rodgers and Shirley Williams, who became known as the Gang of Four. The original SDP merged with the Liberal Party in 1988 to form the Liberal Democrats, but Owen, two other MPs and a minority of party activists formed a breakaway group also called the Social Democratic Party immediately afterwards. That continuing party dissolved itself in the aftermath of a by-election in Bootle, in which the party's candidate received fewer votes than Screaming Lord Sutch's Official Monster Raving Loony Party. However, some SDP activists met and voted to continue the party in defiance of its National Executive, leading to the creation in 1990 of the current Social Democratic Party under the leadership of the candidate who lost that by-election. The party has been led since 2018 by William Clouston.

Ideologically, the party blends social democratic economic policies with cultural conservatism. The party advocates a mixed, social market economy. The party supports a broad welfare state, public ownership of railways and utilities, lower economic inequality, and raising defence spending to 2.5% of GDP. The SDP supports the reintroduction of grammar schools, a more selective education system, abolition of the BBC licence fee, stronger criminal sentencing, and the establishment of a National Care Service to organise and fund social care. It advocates for civic nationalism, an end to mass immigration, withdrawal from the European Court of Human Rights, the Council of Europe, and the 1951 United Nations refugee convention. The SDP campaigned in favour of Brexit in 2016.

In November 2018, the current SDP gained its first and only European parliamentarian when Patrick O'Flynn, Member of the European Parliament (MEP) for East of England, defected from the UK Independence Party. He served in the European Parliament until 1 July 2019. The party's membership includes the journalist Rod Liddle. The SDP control all three council seats in the Middleton Park ward of Leeds after winning the third seat in 2024. In the 2024 South Yorkshire Mayoral election the party's candidate David Bettney received 20,835 votes (7.6%), a 3.7% increase on the previous election.

The party contested the 2024 London mayoral election with candidate Amy Gallagher. The party stood candidates in 122 constituencies in the 2024 general election, where it had an electoral pact with Reform UK in some constituencies. The party campaigned on a manifesto titled 'Homecoming' which pledged to protect "family, neighbourhood and nation".