Throughout his parliamentary career, Mason remained highly involved in the organisation of the Labour Party. He served as its president from 1931 to 1933, and played a major role in policy formulation. Mason was regarded as a social democrat rather than a socialist, and he played a part in moving the Labour Party closer to the political centre. He did, however, believe that the state should have exclusive control over the country's financial system, influenced by social credit monetary reform theories. Other causes supported by Mason include the establishment of a comprehensive old-age pension system and the granting of full state services to naturalised immigrants (the latter making him extremely popular with his electorate's substantial Yugoslavian community).