As the BSP was the main constituent organisation which merged into the newly formed Communist Party of Great Britain, Maclean was alienated from the new party despite his support for the Communist International. He developed a belief that workers in Scotland could develop in a revolutionary direction more swiftly than their comrades in England and Wales, and in 1920 he attempted to found a Scottish Communist Party. This group renamed itself the Communist Labour Party and dropped Maclean's distinctive positions, so he left in disgust. He attempted to found a new Scottish Communist Party, without success. It seems that he may have become a member of the Socialist Labour Party at this time.