The Social Democratic Party (SDP) is a minor political party in the United Kingdom established in 1990. Ideologically, the SDP combines moderate social conservatism with centre-left economic policy and support for a social market economy. Founded by Jack Holmes, it has been led by William Clouston since 2018. In the 2022 local elections, the SDP gained a seat on Leeds City Council and later that year a Derbyshire Dales District Councillor defected to the SDP, giving it a total of two council seats.