Under s 57 of the Constitution, the Governor General has the power to call a double dissolution election (dissolving the entirety of both Houses of Parliament) if a bill is rejected twice by the Senate. There must be an interval of at least 3 months between the two rejections.

By convention, the Governor General does not usually act without the advice of the Prime Minister. Section 57 of the Constitution empowers the Governor General to act unilaterally, however. This power was utilised in the Whitlam dismissal. Alternatively, the Government can request the Governor General to call an early election.

The Governor General is empowered to issue writs for the re-election of every seat in both Houses of Parliament. A double dissolution is the only time that the entire Senate is up for election at the same time. Given that the blocked bill forms the basis for double dissolution, the resulting election effectively becomes a referendum on the issue addressed by the blocked bill. For example, if the Governor General were to call a double dissolution election in response to the Senate’s repeated rejection of the CPRS (Carbon Pollution Reduction Scheme) bill (voted down in August and December 2009 and potentially in February 2010), it is likely to become an election premised largely on climate change. This would be a different to a full-term election, which is likely to be dominated by a myriad of issues.

If, after re-election, the newly formed Senate fails to pass the same bill (after it is passed by the new House of Representatives), the Governor General may convene a joint-sitting of both houses of parliament under s 57. The House of Representatives and the Senate will then debate the bill as one, and the vote will be taken by absolute majority. This is a lower bar, since the increased numbers from the House of Representatives (who have necessarily already passed the bill) will dilute the oppositional numbers in the Senate.

• Parliament of Australia - The Australian Constitution