In 1947 Frey joined the anti-communist Rassemblement du Peuple Français (RPF) ("Rally of the French People") and was a member of the steering committee of the Gaullist movement, in 1951 he became the Treasurer. He sat on the Assembly of the French Union from 1952. He was Secretary General of the National Centre of Social Republicans in 1955. A close colleague of Jacques Soustelle he was active during the crisis of May 1958, preparing for the return of Charles de Gaulle to power. He was appointed to the Constitutional Advisory Committee.