Australian Prime Minister Julia Gillard called a leadership vote after party rivals urged her to step aside in an attempt to stave off defeat in the national elections six month from now.
However, former prime minister Kevin Rudd ruled out a challenge to incumbent Gillard in the vote for the leadership of the Labor Party on Thursday.
Rudd, who was rolled by Gillard in 2010, said he gave his word a year ago that he would not challenge again, and that he would only return to the leadership if drafted with the overwhelming support of the Labor Party.
However, he said, those circumstances did not exist at present.
'Take your best shot'
Gillard's decision to call for the snap vote came after senior cabinet minister Simon Crean openly called for the move with Gillard lagging badly in opinion polls and rampant leadership speculation.
"I have determined that there will be a ballot for the leadership at 4:30pm (0530 GMT) today. In the meantime, take your best shot," she told parliament.
She added that the vote of Labor parliamentarians would also be for the deputy leadership.
Just minutes prior to the vote, former prime minister Rudd, who was brutally ousted by Gillard in mid-2010, said he was not running against Gillard.
He resigned as foreign minister and challenged Gillard for the leadership in February 2012, but lost 71-31 and has since repeatedly pledged not to do so again.
Crean, another former Labor leader and a party elder, cranked up the pressure on Gillard earlier in the day, siding with Rudd and saying the "stalemate has to end" to prevent the party from imploding.
"Something needs to be done to break this deadlock, to resolve the issue once and for all," he told reporters in a second hastily-called press conference of the day in Canberra.
"I am asking her to call a spill (vote) of all leadership positions."
Crean, who warned the leadership speculation was "killing" the party, said he would stand for the deputy leader role, currently held by Wayne Swan.
Crean met with Gillard on Wednesday evening and again on Thursday to inform her of his decision, and said if she won the ballot he would resign.
Asked if she could win the election, Crean said: "The Labor party can win the election."
'No more games'
While Rudd has repeatedly pledged not to make another attempt on the leadership his supporters have been campaigning behind the scenes and Crean said he must declare his intentions.
"He has got no option but to run," Crean said.
"I don't want any more games, I'm sick to death of it, it's about time he stood up and instead of having his camp leak things, actually have the courage of his conviction and his belief.”
Gillard has been dogged by the speculation for weeks, with rumours fuelled by a government decision to try and introduce media reforms which the industry has united to fiercely oppose.
Reports said the government was expected to withdraw its media reform bills from parliament on Thursday in what would be a crushing failure for Gillard.
Some ministers have stressed their loyalty to her, but reports have said any leadership vote between the two would be tight.
Gillard became prime minister in mid 2010 when she ousted Rudd, who at the time had lost the support of powerful factional leaders.
She called an election which she failed to win outright from the surprised public, gaining power only after cobbling together a coalition with a Greens MP and several rural independents to form a majority in the lower house.