Dingle Foot was educated at Balliol College, Oxford, and was called to the bar in 1930. From 1931 to 1945 he was Liberal MP for Dundee. He was Parliamentary Secretary to the Ministry of Economic Warfare in Winston Churchill's wartime coalition, and a member of the British delegation to San Francisco Conference in 1945. At the 1945 election he lost his seat to Labour.
Foot left the Liberal Party and joined the Labour Party in 1956. He was Labour MP for Ipswich 1957-1970. He became Solicitor-General in the government of Harold Wilson and was knighted in 1964. In 1970 he was again defeated, this time by the Conservative Party. His publications included Despotism in Disguis (1937) and British Political Crises (1976).