There was no Communist Party in Great Britain when Lenin wrote "Left-Wing" Communism an Infantile Disorder [LWC](the Communist Party of Great Britain was founded a few months later at the end of July 1920). Nevertheless, Lenin devoted chapter nine of the aforementioned book to discussing the problems of ultra-leftism in Britain. It is not my intention to rehash all the political fights of 1920 surrounding the formation of the CPGB discussed in LWC, instead I will highlight those insights from Lenin that pertain to general principles of Marxism and that are arguably relevant to the struggle for socialism in the early 21st century.
Lenin begins this chapter with a discussion of an article written by Willie Gallacher (1881-1963) published in the "The Workers' Dreadnought" (a publication of one of the groups which were in the process of founding the CPGB) which was full enthusiasm for communism, the Russian Revolution, and the future of the working class in Britain. It also rejected cooperation with the Labour Party and working in the Parliament and the author did not want to cooperate with those who did.
Lenin praised Gallacher's article [he later refers to it as "a letter to the editor"] for expressing the mood, or the temper, of the masses and explained it was just these type of young workers, represented by the author, who would be the future of socialism and who should be supported in all their efforts to build a revolutionary socialist party in Britain. Nevertheless, he does not want them to commit the same errors that the early Bolsheviks made, and that the German party made with respect to ultra-leftism.
The future CPGB would be a formation composed of the coming together of at least four different socialist groups. To build a mass party it would be necessary to work with many other groups of workers at differing levels of class consciousness. Lenin stress that the CPGB, as should be the case with all Marxist parties, has to base its activities on SCIENTIFIC PRINCIPLES: and science, Lenin says, requires two things.
First, a knowledge of what is happening in other countries, capitalist countries, and an analysis of the similarities and differences with your own country and how revolutionaries in those countries have coped with their own conditions. Second, a knowledge of your own country and ALL the groups, classes, parties, etc., and their positions and relationships. The policy adopted, in order to have the greatest number of supporters and best chance of wining, "should not be determined only by the desires and views, by the degree of class-consciousness and the militancy of one group or party alone."
The focus of all this fuss about cooperating and compromising with the bourgeoisie was the Labour Party. The leaders of the Labour Party were considered by the radical workers as sell outs and "social patriots" who would govern in the interests of the capitalists not the workers whom they ostensibly represented and led. Lenin agrees with this and then states "it does not at all follow that to support them means treachery to the revolution; what does follow is that, in the interests of the revolution, working-class revolutionaries should give these gentleman a certain amount of parliamentary support." But why does this follow? Why give any support to false leaders who pose as progressives and really do the dirty work of the enemy? What can Lenin be thinking of?