Opposition Leader Tony Abbott says the resignation of Kevin Rudd as foreign minister confirms that the government is unworthy to continue in office.
"Kevin Rudd has confirmed two things - that the faceless men are running the Labor Party and that the instability at the top of this government is damaging our country," Mr Abbott said in a statement.
"Kevin Rudd's statement tonight confirms that this government is unworthy to continue in office."
Mr Abbott said only the coalition can provide the strong and stable government that will address the issues facing our country and restore hope, reward and opportunity for all Australians.
The surprise announcement was made at a press conference in Washington time at 1.20am local time on Wednesday, with Mr Rudd saying he could not continue as foreign minister because he no longer had the confidence of Prime Minister Julia Gillard.
Key independent MP Tony Windsor said should Mr Rudd become prime minister again, it would most likely lead to an early election.
And if Mr Rudd did try to command a majority on the floor of parliament, he could not rely on Mr Windsor's support.
"If the Labor Party suddenly want to change arrangements in the middle of the stream all bets are off," Mr Windsor told Sky News.
"I'm not going to place myself in the middle of some sort of Fantasy Glades (a theme park) game that's going on and expect to just keep endorsing people whoever the revolving door produces.
"I did a deal with the current prime minister."
Mr Windsor said the negotiations he and fellow independents Rob Oakeshott and Andrew Wilkie held in 2010 on who should form government were with Julia Gillard and Tony Abbott and no one else.
"If one of those parties wants to suddenly change that and act as though they have a majority in the House of Reps that's fair enough," he said.
"But they can't count me in on playing that game."
Mr Windsor said Ms Gillard was doing a good job as prime minister and negotiating Labor's legislation through the parliament.
He said changing prime minister was a high risk strategy that would most likely to lead to an early election "which would only advantage the coalition, probably".
Labor senator Doug Cameron said the "faceless men" in the Labor had forced Mr Rudd's resignation and this was "unacceptable".
"This must just stop within this party," the senator told ABC television. He said these were the same faceless men who set about to replace Mr Rudd as prime minister in 2010.
"It's bad for the party, bad for the nation and bad for the government," he said.
"We just can't afford to have (Opposition Leader) Tony Abbott given a free ride to the prime ministership of this country."
He did not believe Mr Rudd had been campaigning for his old job. His advice to Prime Minister Julia Gillard would be for her express her support and confidence in Mr Rudd and try get him back as the foreign minister.
But he doubted this would happen if the faceless men were "pulling the strings".
Bruce Hawker, a Labor strategist and backer of Mr Rudd, said he would contest the party's leadership.
"That is just my view about it," Mr Hawker told Sky News on Wednesday. "Kevin Rudd is very concerned about the future of the Labor government and the Labor Party, but more importantly what might happen if Tony Abbott become prime minister."
The former foreign minister was popular in the polls and in the electorate, Mr Hawker said.
"He has got real support out in the electorate out there," he said. "It is probably much greater in the electorate than it is in the party room at the moment."
Mr Hawker said backbenchers would consider their self-interest in retaining their seats at the next election when deciding on the Labor leadership.
"When you take everything else away from this equation is whether Kevin Rudd is popular with his colleagues or people get along with him or not," he said.
"One question any backbencher has to ask himself is who is best to lead us to a win against Tony Abbott, because far too much is at stake for the government and the country if Abbott wins the next election."
