with the third party platform, which was adopted in 1920, disagreement within the party grew ever greater. in particular the fact that the platform called for the foundation of a 'dictatorship of the proletariat' during the transitional phase from a capitalist class-based society to a socialist commune sparked violent dispute within the party. in 1921, the party decided not to join the third communist international. the left wing of the party then split from the sp and founded the communist party. in 1926, the sp instead joined the labour and socialist international, which it continued to be a member of until 1940.