He was appointed director of social broadcasts for Radiodiffusion française by Léon Blum but became critical of the Front's economic policies.
In London, he became head of the political section of the Bureau Central de Renseignements et d’Action (BCRA).
After the war, Vallon served as deputy director in Charles de Gaulle's cabinet and held various administrative roles.
He re-entered the Assembly in 1962 under the UNR-UDT coalition and was known for his progressive economic policies, notably his support for worker participation in corporate profits.
He opposed Georges Pompidou's conservatism and supported François Mitterrand in the 1974[1] and 1981 presidential elections, arguing that left-wing principles aligned with the true spirit of Gaullism.