Australian Constitution - Section 64 - Ministers of State & Ministers to sit in Parliament
The Governor-General may appoint officers to administer such departments of State of the Commonwealth as the Governor-General in Council may establish.
Such officers shall hold office during the pleasure of the Governor-General. They shall be members of the Federal Executive Council, and shall be the Queen's Ministers of State for the Commonwealth.
After the first general election no Minister of State shall hold office for a longer period than three months unless he is or becomes a senator or a member of the House of Representatives.