He was elected Member of Parliament for Beckenham at a 1957 by-election, and served until his retirement in 1992.

In his book Referendum (1971), Goodhart argued that the EEC membership referendum, then under discussion in the context of the United Kingdom (UK) joining the European Economic Community (EEC), could in fact serve to entrench constitutional safeguards that the UK lacked, quoting Arthur Balfour's contribution to the debate on the Parliament Bill (later the Parliament Act 1911): "In the referendum lies our hope of getting the sort of constitutional security which every other country but our own enjoys ..." (Referendum, p. 205).

He wrote an account of the 1975 referendum campaign, Full-hearted Consent (1975), and also The 1922: The Story of the 1922 Committee (1973).

He was a member of the Founding Council of the Rothermere American Institute at the University of Oxford.

[2] One of his children is David Goodhart, director of the Demos thinktank and journalist for the Prospect magazine.