Organic centralism is a method of political organisation advocated by left communists

Left communism

Left communism is the range of communist viewpoints held by the communist left, which criticizes the political ideas of the Bolsheviks at certain periods, from a position that is asserted to be more authentically Marxist and proletarian than the views of Leninism held by the Communist International...

, in particular the Italian Left. It was a concept advanced in the Theses of Lyons (1926) in the context of the Third International:

"The communist parties must achieve an organic centralism which, whilst including maximum possible consultation with the base, ensures a spontaneous elimination of any grouping which aims to differentiate itself. This cannot be achieved with, as Lenin put it, the formal and mechanical prescriptions of a hierarchy, but through correct revolutionary politics."

"The repression of fractionism isn't a fundamental aspect of the evolution of the party, though preventing it is.".

This text then argues that fractionalism would have a positive basis, where it arises in response to the relapse of the party into opportunism, as particularly illustrated by Social Democracy

Social democracy

Social democracy is a political ideology of the center-left on the political spectrum. Social democracy is officially a form of evolutionary reformist socialism. It supports class collaboration as the course to achieve socialism...

. It is further argued that bourgeois tendencies are not manifested in fractionalism, but "as a shrewd penetration stoking up unitary demagoguery and operating as a dictatorship from above".

The concept was put forward as against bolshevisation.

"One negative effect of so-called bolshevisation has been the replacing of conscious and thoroughgoing political elaboration inside the party, corresponding to significant progress towards a really compact centralism, with superficial and noisy agitation for mechanical formulas of unity for unity's sake, and discipline for discipline's sake.

This method causes damage to both the party and the proletariat in that it holds back the realisation of the «true» communist party. Once applied to several sections of the International it becomes itself a serious indication of latent opportunism. At the moment, there doesn't appear to be any international left opposition within the Comintern, but if the unfavourable factors we have mentioned worsen, the formation of such an opposition will be at the same time both a revolutionary necessity and a spontaneous reflex to the situation."(ibid)

The concept remains utilized by the International Communist Party

International Communist Party

The International Communist Party is a left communist international political party which is often described by outside observers as Bordigist, due to the contributions by longtime member Amadeo Bordiga...

, which was formed in 1945.

"The meaning of unitarism and of organic centralism is that the party develops inside itself the organs suited to the various functions, which we call propaganda, proselytism, proletarian organisation, union work, etc., up to tomorrow, the armed organisation; but nothing can be inferred from the number of comrades destined for such functions, as on principle no comrade must be left out of any of them.".