British centre-left Liberal Democrat politician, leader of the party in the House of Lords 2001–04. As a member of the Labour party, she was minister for prices and consumer protection 1974–76, and education and science 1976–79. Concerned by the dominance of the Labour Party by its anti-European left wing, in 1981 she was a founder member of the Social Democratic Party (SDP) and served as its president 1982–88. In 1988 she joined the newly merged Social and Liberal Democrats, which became the Liberal Democrats in 1989.
When Labour returned to power in March 1974 she entered the cabinet as secretary of state for prices and consumer protection, and became secretary of state for education and science from 1976. Strongly pro-European and a moderate ‘social democrat’, Williams was one of the ‘Gang of Four’ of prominent Labour politicians who left the party because of its swing to the left and co-founded the SDP in 1981. She became the SDP's first elected member of Parliament (MP) when she won the Crosby by-election in 1981, but lost the seat at the 1983 general election.
The daughter of the socialist writer Vera Brittain, she was educated at St Paul's Girls' School, Somerville College, Oxford, and Columbia University, New York. She began her career as a journalist and was general secretary of the Fabian Society 1960–64. She was elected Labour MP for Hitchin in 1964, and was MP for Hertford and Stevenage 1974–79. Between 1966 and 1970 she held junior positions in the government (for labour, education, and home affairs). From 1970 to 1974 Williams was opposition spokesperson for social services, home affairs, and prices and consumer protection.
After marrying the American politics professor Richard Neustadt (1919–2003) in 1987, she divided her time between the UK and the USA, where she lectured on politics at the John F Kennedy school of government at Harvard University 1988–2000. She was made a life peer in 1993.