He stood for the Liberal Party at numerous Parliamentary elections: in Merton and Morden in 1950, Bethnal Green in 1951 and 1955, and Gainsborough in 1959 and 1964. By this time, he was serving on the council of the Liberal Party. In the run-up to the 1975 United Kingdom European Communities membership referendum, Douglas chaired the Liberal "No to the Common Market" Campaign.