The challenge to Taoiseach Brian Cowen's leadership was sparked by his handling of crisis talks ahead of Ireland's multi-billion bailout, Foreign Affairs Minister Micheal Martin claimed today.
Mr Cowen will test his support to head his Fianna Fail party in a secret ballot this evening with Micheal Martin leading the revolt.
Mr Martin claimed the lack of communication around talks with the International Monetary Fund and European chiefs last November was a watershed.
"The management of the IMF, the presentation of the IMF coming into the country, that to me was a watershed moment," Mr Martin said.
"I think the way that was managed and communicated and ministers came out, from my information, without the full knowledge of what actually was going on at that time."
The Taoiseach and Government were roundly criticised after two senior ministers denied talks were taking place over a possible bailout while Brussels officials were briefing otherwise.
But Mr Cowen hit back, claiming the Cabinet had been kept informed all along.
He also described criticism over the handling of the affair, which saw Ireland accept an €85bn bailout, as a lazy political narrative.
The Taoiseach needs the support of 36 TDs when he puts forward a motion of confidence in himself at a Fianna Fail parliamentary party meeting in Leinster House.
Mr Martin has tabled his resignation over the leadership question but it is unclear if he will leave the Cabinet if Mr Cowen remains leader of Fianna Fail.
The Government has less than three months to run, with a General Election pencilled in for March 25.
Mr Cowen has come under intense scrutiny in the last week over previously undisclosed contacts with former Anglo-Irish Bank chairman Sean FitzPatrick.
Both he and Mr Martin, who gave separate interviews on RTE Radio, have denied the Anglo links are at issue.
But record low 14pc poll ratings are. And Mr Martin also warned that the lack of focus on the looming election, the failure to manage the retirement of more than a dozen Fianna Fail TDs in the last few months, and the handling of the IMF crisis all sparked his decision to move against the Taoiseach.
Mr Cowen hit back over questions around the bailout: "Absolutely we told the whole Cabinet in respect of what the options were, what the situation was."
Mr Martin said the real catalyst in his decision to take on Mr Cowen was the lack of an election machine.
"I said to myself personally I'll be damned if I'm going to run in a campaign that has no fire in the belly, that there's no electoral machine in preparation, that there was no sense that we can mount a vigorous campaign and that morale was sapping within the organisation," the minister said.
Mr Cowen repeated that he was confident he would survive the motion and said he believes good can come from the vote.
"I think it's been a good exercise because it helps to bring clarity to the situation about which there has been some debate in the party, and I want to get it clarified and the party move on and unite behind the decision, whatever it is," he said.
"And I'll respect the decision."
Mr Martin revealed yesterday that discontent with Mr Cowen has been damaging the party for almost a year.
The Taoiseach appears on course for a narrow victory after retaining the support of most of his Cabinet.
Justice Minister Dermot Ahern - in hospital following an operation - was the latest ally to declare for Mr Cowen.
Sources close to the retiring TD confirmed he would support the Taoiseach with Fianna Fail officials expected to give Mr Ahern the opportunity to cast his vote in the secret ballot from outside the meeting.
Others in the Cowen camp include Tanaiste Mary Coughlan, Social Protection Minister Eamon O Cuiv - although he has also expressed leadership ambitions himself - Enterprise Minister Batt O'Keeffe, Agriculture Minister Brendan Smith, Gaeltacht Minister Pat Carey and Children's Minister Barry Andrews. Government Chief Whip John Curran is also on side.
Finance Minister Brian Lenihan - himself a leadership contender - is expected to announce his decision at lunchtime.
Including backbenchers, Mr Cowen looks as though he has half the party; however, about 20 TDs have yet to declare their hand.