Tankie was a pejorative

Pejorative

Pejoratives , including name slurs, are words or grammatical forms that connote negativity and express contempt or distaste. A term can be regarded as pejorative in some social groups but not in others, e.g., hacker is a term used for computer criminals as well as quick and clever computer experts...

 term referring to members of the Communist Party of Great Britain

Communist Party of Great Britain

The Communist Party of Great Britain was the largest communist party in Great Britain, although it never became a mass party like those in France and Italy. It existed from 1920 to 1991.-Formation:...

 who followed the Kremlin

Kremlin

A kremlin , same root as in kremen is a major fortified central complex found in historic Russian cities. This word is often used to refer to the best-known one, the Moscow Kremlin, or metonymically to the government that is based there...

 line, agreeing with the crushing of revolts in Hungary and later Czechoslovakia by Soviet tank

Tank

A tank is a tracked, armoured fighting vehicle designed for front-line combat which combines operational mobility, tactical offensive, and defensive capabilities...

s. Detractors accused the Soviet Union

Soviet Union

The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....

 of social-imperialism

Social-imperialism

Social-imperialism is a Marxist expression, typically used in a derogatory fashion, to describe people, parties, or nations that are "socialist in words, imperialist in deeds"...

.

The term originated from 1956, when the CPGB lost a lot of members, who left in protest at the Soviet invasion of Hungary. Those who left either became part of the anti-revisionist

Anti-Revisionist

In the Marxist–Leninist movement, anti-revisionism refers to a doctrine which upholds the line of theory and practice associated with Karl Marx, Friedrich Engels, Vladimir Lenin and Joseph Stalin, and usually either Mao Zedong or Enver Hoxha as well...

 movements, embraced Trotskyism

Trotskyism

Trotskyism is the theory of Marxism as advocated by Leon Trotsky. Trotsky considered himself an orthodox Marxist and Bolshevik-Leninist, arguing for the establishment of a vanguard party of the working-class...

, or left Communism

Communism

Communism is a social, political and economic ideology that aims at the establishment of a classless, moneyless, revolutionary and stateless socialist society structured upon common ownership of the means of production...

altogether.