| | | | Democratic Federation 1881-1884 | | Labour Emancipation League 1881-1884 |
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| | | | | | Social Democratic Federation 1884-1911 | |
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Socialist League 1885-1901 | | Socialist Union 1885-87 | | | | | | Socialist Labour Party 1903-80 | | | | | Socialist Party of Great Britain 1904-present | |
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| | | | | | | | | | | | | | | | | | | | Socialist Propaganda League 1911-51 | | Socialist Party of Great Britain (Reconstituted) 1991-present |
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| | | | | British Socialist Party 1911-20 | | South Wales Socialist Society 1911-20 | | | Industrialist League 1908-10s |
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Socialist National Defence League 1915-23 | | National Socialist Party 1916-20s | | | | | | | | | | | | | | | | British Section of the International Socialist Labour Party 1910s-37 |
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| | | | | | | | | | | Communist Party of South Wales and the West of England 1920 | | | | | | | | | | |
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Workers Socialist Federation 1913-20 | | | | | | | | | | | | | | | | | | | | | |
| | | | | Communist Labour Party 1920-21 | | | | | | | Communist Unity Group 1920 | | Communist League 1919-20 | | |
Communist Party (British Section of the Third International) 1920-21 | | | | | | | | | | | | | | | | | | | | | | |
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| | | | | | | | | | | | | | | | | | Anti-Parliamentary Communist Federation 1921-45 | | |
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| | | | | | | | Communist Party of Great Britain 1920-90 | | | | | | | | | | |
| | | | | | | | | | | | | | | | | | United Socialist Movement 1933-65 | | |
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| Communist Workers Party 1921-24 | | Fife Socialist League 1953-64 | | | | | Communist League 1932-35 | | | | | | |
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| | | | | | | | | | | | Marxist Group 1934-38 | | Marxist League 1935-38 | | | |
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| | | Committee to Defeat Revisionism, for Communist Unity 1963-60s | | | | | | | | | | | | | | | | | | |
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| | | | | | | | | | | | | | Militant Group 1935-38 | | | | | | | | | |
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| | | Workers Party of Scotland 1967-90s | | Working People's Party of England 1968-85 | | | | | | | | | | | | | | | |
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| | | | | | | | | | | | | Workers International League 1937-44 | | | | | | | | | |
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Communist League of Great Britain 1965-present | | Joint Committee of Communists 1968-69 | | | | | | | | | | Revolutionary Socialist League 1938-44 |
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Communist Federation of Britain (Marxist-Leninist) 1969-77 | | Communist Workers League of Britain (Marxist-Leninist) 1969-81 | | | | | | | | Revolutionary Workers League 1940-41 | | | Socialist Workers Group 1941-44 | | Left Fraction (British Section of the Fourth International) 1943-60s |
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| | | Communist Unity Association (Marxist-Leninist) 19??-77 | | Communist Party of Britain (Marxist-Leninist) 1968-present | | | | | | | Revolutionary Communist Party 1944-50 |
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| | | | | | | Communist Workers' Movement 1976-80 | | | The Club 1947-59 | | | | | | | | Socialist Review Group 1951-62 |
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| Revolutionary Communist League of Britain 1977-98 | | | | | | | | | Socialist Labour League 1959-70s | | | | Revolutionary Socialist League 1953-64 | | International Socialists 1962-77 |
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| | | | | Revolutionary Marxist-Leninist League 1968-80 | | | | | | | | | |
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| | | | | | | | | | | | | | | | Solidarity 1960-81 |
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| Association of Communist Workers 1969-97 | | Marxist-Leninist Workers Association 1971-?? | | | |
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| Appeal Group 1971-76 | | New Communist Party of Britain 1977-present | | | |