Prime Minister Julia Gillard will today announce that she is calling a ballot to resolve the Labor leadership stoush with her predecessor Kevin Rudd.

Ms Gillard will hold a morning press conference in Adelaide to call a caucus ballot for Monday, when Parliament resumes.

Overnight she criticised Mr Rudd over his sudden resignation as Foreign Minister, saying she was "disappointed" he did not speak to her before his announcement.

"I am disappointed that the concerns Mr Rudd has publicly expressed this evening were never personally raised with me, nor did he contact me to discuss his resignation prior to his decision," she said in a statement.

This morning Attorney-General Nicola Roxon told ABC News Breakfast that a leadership spill was inevitable, and predicted an easy win for Ms Gillard.

While Ms Gillard was measured in her five-paragraph statement last night, the developments unleashed a vitriolic response from her deputy Wayne Swan.

"The party has given Kevin Rudd all the opportunities in the world and he wasted them with his dysfunctional decision-making and his deeply demeaning attitude towards other people, including our caucus colleagues," he said in a statement.

"He sought to tear down the 2010 campaign, deliberately risking an Abbott prime ministership, and now he undermines the Government at every turn.

"He was the party's biggest beneficiary then its biggest critic, but never a loyal or selfless example of its values and objectives."

Mr Rudd resigned in Washington at a snap press conference called in the middle of the night.

He said he would not be part of the leadership "soap opera" and that resigning was the only "honourable" thing for him to do.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 5 minutes 22 seconds 5 m Kevin Rudd resigns ( ABC News )

His surprise move came as a growing number of Gillard supporters called for the Prime Minister to confront Mr Rudd and sack him if he refused to pledge his loyalty.

By resigning, Mr Rudd pre-empted any plan to dismiss him while leaving open the possibility of launching a leadership challenge from the backbench.

Significantly, that is something Mr Rudd failed to rule out during his press conference.

Mr Rudd said he would return to Brisbane on Friday to consult his family, community and colleagues about his future and would reveal his intentions before Parliament resumed on Monday.

The former prime minister, who was ousted from the job by Ms Gillard in June 2010, denied he had been plotting a comeback.

"There's no way, no way that I would ever be party to a stealth attack on a sitting prime minister elected by the people," he said.

"We all know that what happened then was wrong and it must never happen again."

Mr Rudd said he had to conclude he no longer had the confidence of the Prime Minister following a string of public attacks from senior Gillard supporters.

'Faceless men'

Sorry, this video has expired Democracy requires leadership ballot to wait: Cameron ( Tony Jones )

Labor Left powerbroker Doug Cameron has come out in support of Mr Rudd, laying the blame for his resignation at the feet of the "faceless men" of the party.

But he says the ballot should be held on Friday, to give Mr Rudd a fair chance to marshal support from the Labor caucus.

He says he does not think Ms Gillard is capable of defeating Tony Abbott in an election.

"If there is a spill, I think Kevin Rudd is the best chance of the Labor party ensuring that Tony Abbott doesn't become the Prime Minister of this country," he said.

"I think that's a disaster for the nation, it's a disaster for a progressive policy agenda that the Labor party is pursuing."

Senator Cameron harshly criticised the ministers who have attacked Mr Rudd since his resignation.

"I can't speak for the Prime Minister, but it's clear that some senior ministers are intent on putting a stake through Kevin Rudd's heart, and I don't think that's justified."

But Trade Minister Craig Emerson says he has little sympathy for Mr Rudd's complaints that members of cabinet have attacked his credibility.

"For Kevin then to say that this bickering and destabilisation must stop, well there's a good idea, there's a great idea," he told Lateline.

"He started it way back in the last election. It's been going on ever since and now at least it's coming to a point of resolution."

Opposition Leader Tony Abbott says the instability at the top of the Government is damaging Australia.

"Kevin Rudd's statement tonight confirms that this government is unworthy to continue in office," he said in a statement.

"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."