Prime Minister of Australia prime minister, otherwise William McMahon63. Robert Menzies was the oldest person to ever be prime minister, leaving office at 71 years old. The longest-serving Prime Minister was Sir Robert Menzies, who served in office twice: from 26 April 1939 to 28 August 1941, and again from 19 December 1949 to 26 January 1966. In total Robert Menzies spent 18 years, 5 months and 12 days in office. He served under the United Australia Party and the Liberal Party respectively. The shortest-serving Prime Minister was Frank Forde, who was appointed to the position on 6 July 1945 after the death of
Department of the Prime Minister and Cabinet (Australia) Department of the Prime Minister and Cabinet (Australia) The Department of the Prime Minister and Cabinet (PM&C) is an Australian Government public service central department of state with broad ranging responsibilities, primary of which is for intergovernmental and whole of government policy coordination and assisting the Prime Minister of Australia in managing the Cabinet of Australia. The PM&C was established in 1971 and traces its origins back to the Prime Minister's Department established in 1911. The role of PM&C is to support the policy agendas of the Prime Minister and Cabinet through high quality policy advice and the coordination of