Pearce filled a number of different roles for the CPGB; from 1953 to 1960, he was Secretary of the Birmingham City area, then he became Secretary of the Welsh District of the CPGB, serving until 1984. Following the Prague Spring of 1968, he began to be critical of the Soviet Union, and was vocal on his support for Welsh devolution. He also served on the editorial board of "Marxism Today", and on the CPGB's Executive Committee.