A member of the Labour Party from 1918, he was a defender of the Soviet Union. In 1932, as part of G. D. H. Cole's New Fabian Research Bureau's expert commission of enquiry, he visited the Soviet Union, and, according to Margaret Cole, "the eminent KC swallowed it "all"". Pritt was expelled from the Labour Party in March 1940 following his support of the Soviet invasion of Finland.