Around this time, he also served as secretary of the International Arbitration Association, and of the Friends of Russian Freedom.
A supporter of Victor Fisher, he followed him into the British Workers League, before joining the National Democratic and Labour Party (NDP).
[2] Standing as a candidate of the NDP, with support of the Liberal-led and Conservative-dominated coalition government, Green contested the newly created Leicester West constituency at the 1918 general election.
His only opponent was the Labour Party candidate Ramsay MacDonald, a sitting MP for the two-seat Leicester constituency until it was divided for this election.
[4] However, at the 1922 general election, without coalition support, Green stood as a National Liberal Party candidate.