The early Society rapidly expanded to include solicitors of a more radical persuasion. Its two most prominent office-holders in the 1930s were Stafford Cripps QC (Labour MP since 1931) and D N Pritt QC (elected as a radical Labour MP in 1935). Pritt was commemorated for many years in the Society’s annual D N Pritt Memorial Lecture.
Throughout the 1930s, the Society worked closely with the National Council for Civil Liberties (now Liberty, founded in 1936) and issued a number of progressive legal publications through the Left Book Club (set up by Victor Gollancz). It was affiliated to the Labour Party and its members included Labour Party and Communist Party members.
Records surviving from 1942 show the Society publishing proposals for law reform 'The Law and Reconstruction' covering legal aid, workmen’s compensation, the appointment of magistrates, criminal procedure, divorce, costs of appeals and various other subjects, including very technical proposals (notably "an application of the Admiralty rule of division of loss to cases of motorcar accidents and the like"). There was also a less than critical approach to 'Soviet justice' with a number of publications describing, in approving terms, the Soviet judicial system. Like so many intellectuals of the time, the Haldane Society closed its eyes to the nature of Stalin’s terror.