A snap election will be called next Tuesday unless Fianna Fail backs off embattled Tanaiste Frances Fitzgerald, Taoiseach Leo Varadkar has said.
Voters may be going to the polls before Christmas - and at a crucial moment in the Brexit negotiations.
Mr Varadkar is due to travel to Brussels on December 14 to hammer out a deal with the UK for the future of the Border region. However, he is now likely to be in the middle of an election campaign at home.
In his first public comments since Fianna Fail tabled a motion of no confidence in the Tanaiste, Mr Varadkar said he will stand by her in the days ahead.
He accused opposition TDs of trying to carry out a "summary execution" without knowing all the facts.
"I don't believe the decapitation of the Tanaiste based on the trumped-up charges is fair," he said.
Asked on RTE's Six One News why he would not ask Ms Fitzgerald to step aside in the national interest, Mr Varadkar said that would be "throwing a good woman under the bus for political expediency, to save myself and my Government".
The Taoiseach confirmed that if the massive gulf between Fine Gael and Fianna Fail cannot be resolved by Tuesday, then the country will go to the polls.
"We still have opportunity for the next few days to avoid an election," he said.
"Certainly I don't want there to be a general election."
However, he gave no indication that he would cede ground to Fianna Fail leader Micheal Martin in the dispute.
"I think fundamentally this had to be about truth, justice and fairness," the Taoiseach added.
He described the case against Ms Fitzgerald - that she did not act on an email alerting her to legal rows at the O'Higgins Commission - was "flimsy".
According to well-placed sources, a meeting between Mr Varadkar and Mr Martin yesterday was "more civil than some previous ones" but ultimately made no progress.
Having failed to convince Mr Varadkar to ask his deputy to step down, Fianna Fail is expected to now turn up the pressure on Ms Fitzgerald to offer her resignation.
She continues to argue that she acted appropriately at all times when dealing with whistleblowers and could not have intervened on foot of an email to stop gardai adopting an aggressive legal approach at the O'Higgins Commission.
However, Fianna Fail finance spokesman Michael McGrath said the Tanaiste "has a hugely important personal decision to make".
"If the Taoiseach isn't going to ask her to resign, it's a decision she'll have to make herself and it will have national consequences," he said.
Mr Varadkar's hand was strengthened by support from the Independent ministers in Government, who met him in Government Buildings to discuss the growing crisis last night.
Transport Minister Shane Ross raised concerns that the country was being forced into a "needless and costly general election".
Mr Ross said it would be "disproportionate" for the Tanaiste to be removed from office because of an email.
"Going to the country in the weeks before Christmas is not what the country either needs or wants," he said.
"It seems possible, even likely, that it could take months for another government to be formed."
The minister was flanked by Kevin 'Boxer' Moran, Finian McGrath, John Halligan and Sean Canney, as he warned the upcoming Brexit talks were more important than the current controversy.
Mr Moran launched a blistering attack on Fianna Fail and Sinn Fein, which have both tabled motions of no confidence in Ms Fitzgerald.
He said the group has 100pc confidence in her and suggested the two opposition parties were merely trying to set up their own government.
"Look at the papers from last week, you had people from Fianna Fail looking to go into government with Sinn Fein," Mr Moran said.
"Now they're pushing for that and they put pressure on Micheal Martin here today. We are on the brink of a Fianna Fail/Sinn Fein new policy document, new government. Is this what they are planning?
"This is wrong. We deserve to give the people leadership."
Mr Moran went on to question why Fianna Fail was taking such a hard line when this month seven years ago "they were the party that told the people of this country that the IMF wasn't in this country".
Despite all sides saying they wished to avoid a general election, massive efforts are being made behind the scenes to prepare for one.
Fianna Fail has already held a substantial number of selection conventions around the country and is well positioned to launch an early campaign.
Fine Gael has only formally selected candidates in Dublin Rathdown, Dublin North West and Longford/Westmeath. Its National Executive is ready to fast-track conventions nationwide.
Sinn Fein confirmed yesterday that Mary Lou McDonald would lead its election campaign in the wake of Gerry Adams's decision not to put his name forward in Louth.
Labour leader Brendan Howlin said his party was "election ready".