The CWI was founded in 1974 by supporters of what was then called the Militant Tendency in Britain, Sweden, Ireland and several other countries. Until the early 1990s CWI sections persued a policy of entrism into social democratic or labour parties but this largely ended in the 1990s due to an analysis that these parties had become bourgeoisified and were no longer mass workers parties. This was strongly resisted by Ted Grant, Militant's founder, who left in 1992 and formed the Committee for a Marxist International.
Since their open turn CWI sections have, in a number of countries, run candidates under their own name electing Joe Higgins to the Irish Dáil Éireann as the Socialist Party as well as several councillors in Britain, specifically in London and Coventry. The CWI also has elected members of national or regional legislatures or local councils in Sweden, Germany, Australia, the Netherlands (members of the Dutch Socialist Party who are also CWI members) and in the ex-Soviet Union.
CWI members also played a leading role in founding the Scottish Socialist Party though, due to a split, leading SSP members such as Tommy Sheridan are no longer in the CWI.