International Marxist Group
The International Marxist Group, a section of the Trotskyist Fourth International, Unified Secretariat, emerged in the mid 1960s the journal 'The Week'. It began as an entryist group working within the Labour Party, before breaking away in 1968.
In 1977 its newspaper, 'Socialist Challenge', first appeared. Its membership peaked in the 1970s at around 1000 but by 1983 its membership had fallen to around 700.
In the early 1980s it reverted back to entryism although it chose not to refer to its members or branches within the Labour Party, instead referring to 'Socialist Challenge' supporters. In December 1982 the Group changed its name to the Socialist League and its associated newspaper from 'Socialist Challenge' to 'Socialist Action'. By 1990 the circulation of 'Socialist Action' was around 500.
- International Marxist Group (IMG), later the Socialist League, Modern Records Centre, University of Warwick.
- Christopher Andrew, The Defence of the Realm: The Authorized History of MI5, Allen Lane, 2009, p.660.