The Bolshevik trade union debate of 1921 could be seen as a semi-parliamentary practice both in its form and content. Various groups and platforms participated in this discussion, using it as a tribune for spreading their views among the members of the party. This article examines the course of the discussion in the Petrograd party organization: especially, its form, representation, and the conflicts that it produced. Petrograd Bolsheviks saw the discussion not only as a space for a free circulation of opinions but also as a place for propaganda and political conflict. During debates, both of the rival platforms in the city (the supporters of Vladimir Lenin and the supporters of Lev Trotskii) tried to impugn the actions of each other. The party press also acted not as an impartial observer of the controversy but actively formatted a vision of the domination of Lenin’s adherents in the discussion. Such a process brought discussions in the Bolshevik party close to the practice of a parliamentary debate, and produced a situation that I term ‘semi-parliamentarism in one party’.