A late switch by Labor back to Kevin Rudd could provoke a constitutional crisis forcing Governor-General Quentin Bryce to consider options such as a sudden recall of Parliament to test Labor's majority or even the appointment of Tony Abbott as prime minister.

Another option would be the commencement of an immediate caretaker period before an early election.

Pressure is building within Labor for a leadership showdown between Kevin Rudd and Prime Minister Julia Gillard Credit:Andrew Meares

With pressure building within Labor for a leadership showdown between Mr Rudd and Prime Minister Julia Gillard, strategists on both sides of politics are waking up to the risk of unintended consequences of a leadership change in a party that does not have a majority in the House of Representatives. Legal experts say the Governor-General would be in uncharted waters because a new Labor leader would not necessarily command a parliamentary majority.

University of NSW law professor George Williams said there would be several possibilities arising from a change, beginning with independent MPs Tony Windsor and Rob Oakeshott ''grudgingly indicating their support'', in which case Mr Rudd would be signed in as prime minister. Another option would see the independents switch to Opposition Leader Mr Abbott, in which case he would be made prime minister, while a third possibility is that their allegiance becomes unclear.