Greenwood joined the Labour Party at the age of 14 and was a prospective candidate for
Colchester before the war. He led the Labour group on
Hampstead Borough Council from 1945 until 1949, and entered Parliament as member for
Heywood and Radcliffe in
a by-election in February 1946. Following boundary changes, he moved to represent
Rossendale in 1950. He was vice-chairman of the
Parliamentary Labour Party in 1950–51, and was in the Shadow Cabinet from 1951 to 1952 and from 1955 to 1960. He also served on the party's
National Executive Committee from 1954 to 1970, In 1965 he was moved to become
Minister of Overseas Development, and the following year he became
Minister for Housing and Local Government, in which he oversaw a record 400,000 houses built during 1966-67. In October 1969 he was dropped from the cabinet when his housing ministry was placed under the expanded
Department of Local Government and Regional Planning headed by
Anthony Crossland. From 1977 to 1979 he was Chairman of the House of Lords Select Committee on the European Communities and Principal Deputy Chairman of Committees. ==Business career==