 In 1956, he was nominated Secretary of State for Foreign Affairs in Guy Mollet's cabinet, but resigned due to his opposition to the repressive policy of Mollet in Algerian War (1954–62) and to the arrest of Ahmed Ben Bella.He left the SFIO in 1958, because of the party's support for Charles de Gaulle's comeback and for the new Constitution elaborating a presidential regime (the Fifth Republic).With Pierre Mendès-France, he founded the dissident Autonomous Socialist Party (PSA) which became, in 1960, the Unified Socialist Party (PSU).