Section 57 of the Commonwealth Constitution details the conditions for a double dissolution:
More than one Bill may act as a trigger for a double dissolution. A double dissolution can only happen when there is a deadlock between the two houses of Parliament and it usually occurs at the request of the Prime Minister.
In a double dissolution, the Governor-General dissolves both the Senate and the House of Representatives at the same time, meaning every seat in both chambers is contested. This is the only time that all senators stand for election at the same time.
There have been six double dissolutions of the Australian Parliament: in 1914, 1951, 1974, 1975, 1983 and 1987.
The most famous of these double dissolutions occurred in 1975. The Senate refused to pass the supply of the government (Budget Bills), led by Prime Minister Gough Whitlam. This caused a deadlock which could be used as a double dissolution trigger. The Prime Minister did not want a double dissolution election; however, Governor-General Sir John Kerr dismissed the government and an election was called by caretaker Prime Minister Malcolm Fraser.
After a double dissolution election, the Bill(s) which triggered the double dissolution may be presented to both houses of Parliament again. If a deadlock occurs once more, the Governor-General may order a joint sitting of both houses of Parliament. At a joint sitting, all Members of Parliament from both houses meet together to vote on the Bill(s). A joint sitting has only occurred once in the Australian Parliament namely, in 1974 in the government headed by Prime Minister Gough Whitlam.
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