Frey was Secretary General of the Union for the New Republic (Union pour la nouvelle République, UNR) from 1958 to 1959 and was attached to the cabinet of Jacques Soustelle, then Minister of Information. He himself was the Minister of Information from 8 January 1959 to 5 February 1960 and Minister Delegate to the Prime Minister Michel Debré until 6 May 1961, before being appointed interior minister from May 1961 until April 1967 (law Debre and Georges Pompidou). He fought against the Organisation armée secrète (OAS) at the end of the war in Algeria.