In 1935, Marsden joined the Communist Party of Great Britain (CPGB), radicalised in opposition to the Italian invasion of Abyssinia. He also joined the Constructional Engineering Union, serving as a site steward for more than thirty years.
In 1952, Marsden was elected to the executive of the union, representing North West England, and in 1962 he became the union's full-time organiser for the region, also representing the union on the executive of the Confederation of Shipbuilding and Engineering Unions. Meanwhile, he became increasingly prominent in the CPGB, serving on its Lancashire and Cheshire District Committee, and standing unsuccessfully for the party in the 1963 Manchester Openshaw by-election, and again in the seat in the 1964 and 1966 UK general elections. In 1968, he was elected to the party's Executive Committee.
Marsden was elected as general secretary of the union in 1968. Three years later it became part of the Amalgamated Union of Engineering Workers, albeit remaining largely autonomous, with Marsden continuing as general secretary of the union's new Construction section. This gave Marsden increased prominence in the trade union movement, and he was a prominent figure at meetings of the Trades Union Congress.
Marsden died in 1975, still in office.
- England & Wales, Civil Registration Death Index, 1916-2007
- Graham Stevenson, "Marsden Eddie", Compendium of Communist Biography
- Trades Union Congress, "Obituary: Eddie Marsden", Annual Report of the 1975 Trades Union Congress
- New Society, Vol.27, p.120
- Robert Taylor, The Fifth Estate: Britain's Unions in the Seventies, p.83
- F. W. S. Craig, British Parliamentary Election Results 1950–1973
- Exton, Jack; Gill, Colin (1981). The Trade Union Directory. London: Pluto Press. pp. 92–95.
|Trade union offices|
| General Secretary of the Constructional Engineering Union
| General Secretary of the Amalgamated Union of Engineering Workers (Construction Section)