The Communist Party of Britain (Marxist-Leninist) (CPB(M-L)) is a British communist political party. The small party was formed in 1968 by Reg Birch as a split from the Communist Party of Great Britain, siding with the Communist Party of China. Originally planned as the "British Marxist Leninist Organisation", the party published the Worker from 1969 until 2000, when it became Workers. In 1976, the Communist Workers' Movement split from the CPB(M-L), later joining its main British rival, the Revolutionary Communist League of Britain.
More recently, the CPB (M-L) has developed a national line for Britain. The party is strongly opposed to the European Union. Like the New Communist Party of Britain, the CPB(M-L) supported Labour in elections to bring about the removal of the Thatcher government, and has continued to call for votes for Labour since.
CPB(M-L) has an extremely low public profile, with its members focusing on work in the labour movement. However, the party has lost many of its leading trade union activists in recent years, such as NUT activist Bill Greenshields, now a member of the Communist Party of Britain.
It should not be confused with the Communist Party of Britain, the Revolutionary Communist Party of Britain (Marxist-Leninist), nor with the Communist Party of Great Britain (Marxist-Leninist).