He was the 21st prime minister of Australia, serving from December 1972 to November 1975. To date the longest-serving federal leader of the Australian Labor Party (ALP), he was notable for being the head of a reformist and socially progressive government that ended with his controversial dismissal by the then-governor-general of Australia, Sir John Kerr, at the climax of the 1975 constitutional crisis. Whitlam remains the only Australian prime minister to have been removed from office by a governor-general.