Malcolm Turnbull, Brendan Nelson and 84 other Liberal MPs are locked in a meeting to decide the party's leadership.
Dr Nelson called the surprise leadership spill at a party meeting last night.
Most Liberal MPs arriving at parliament this morning have said it's a gutsy move that caught them all on the hop.
Peter Costello has also strengthened Nelson's bid with his endorsement.
WA Liberal backbencher Barry Hass has summed up the view of many who have stopped to talk when asked if he'll be voting for Dr Nelson.
“Abso-bloody-lutely, as they say in the classics,” he said.
“He’s a helluva nice guy, he’s run a good leadership and he’s done the right thing by Australians.”
6:00 AM
A surprise call of a leadership ballot will see Brendan Nelson and Malcolm Turnbull fighting for control of the party this morning.
At nine o’clock this morning the leadership at the Liberal party will be declared vacant.
A vote will follow, shaping to be a contest between Brendan Nelson and Malcolm Turnbull.
It was a shock call by Dr Nelson last night – responding to rumours and innuendo within the party.
He announced the ballot to the amazement of colleagues – almost immediately he gained the support from Peter Costello, who said he deserves a clean run.
As of now Mr Costello is not running for any significant role.
Just after the election, only three votes separated Dr Nelson and Malcolm Turnbull for the Liberal leadership.
Dr Nelson said on Monday night he remained determined and committed to the future of the Liberal Party and the nation.
"But as we move forward, I am asking our party to draw a line in the sand and mark a transition - from the difficult aftermath of an election defeat to the building and presentation of a credible, attractive and inspiring alternative government," he said.
"In doing so, we will make a renewed commitment to unity and discipline, to focus less on internal preoccupations and more on the Rudd government, policy and the important issues concerning everyday Australians."
The position of the deputy Liberal leadership also remains unclear.
Julie Bishop has not indicated she plans to stand aside from her position but has said previously she would happily work with either Dr Nelson or Mr Turnbull.
However, during today’s meeting, one of her colleagues could call for a spill of the position.
The matter would then have to go to the vote.