A member of the Communist Party, Gardner was a leading official of the National Union of Foundry Workers (long since subsumed in the mergers that led to Unite the union *see below).
Garner was narrowly defeated in the election for General Secretary of the NUFW in the spring of 1943, by Albert Wilkie, with 8,024 votes to 7044. In December 1944, Jim Gardner won though in his candidature for the post, defeating Tom Colvin in the second ballot by 10,900 votes to 9,562.
A prominent Communist trades union official throughout the Cold War, he was a leading advocate of national strike action in the Confed pay claim of 1953-4. Gardner was no longer general secretary by 1958.
NOTE ON MERGERS AND THE FOUNDRY WORKERS
In 1967, the Amalgamated Union of Foundry Workers merged with the Amalgamated Engineering Union. Becoming the foundry section of the Amalgamated Union of Engineering and Foundry Workers, after further mergers with the Constructional Engineering Union and the Draughtsmen and Allied Technicians' Association in 1970 it became the foundry section of the Amalgamated Union of Engineering Workers. Some of the sections of the AUEW merged and later formed the AEU, then the AEEU, which merged with MSF to form Amicus, which merged with the T&G to form Unite.