There will be no election before 2020 after Fianna Fáil "reluctantly" concluded that Ireland cannot afford to have an election amid Brexit uncertainty.
Micheál Martin has told the Dáil today "business as usual is not acceptable".
While criticising Taoiseach Leo Varadkar’s government for being complacent on key issues such as housing, Mr Martin said: "The chaos will not spread here from London… The national interest will come first."
The details of the arrangement will still have to be negotiated but the Fianna Fáil leader said his party will help pass a budget next year. He indicated an election would then take place in early 2020.
Mr Martin said under normal times there would be an immediate election – but "these are not normal times and Ireland is immediately confronted with one of the biggest threats in many decades".
He noted that a lengthy election campaign was likely to result in months of negotiations before a new government is formed.
And on that basis he was publicly offering an "unprecedented" level of stability for a minority government. He said it was a tough decision but the "right one for Ireland".
Speaking about the chaotic scenes emerging from Westminster, Mr Martin said: "This period of growing chaos and uncertainty is not one we can assume comes to an end by March 29."
And he insisted that Irish politics would not be affected by the same sense of drift at a time when the risk of no deal had risen "dramatically".
In his contribution prior to Mr Martin’s speech, Taoiseach Leo Varadkar said it was "noteworthy to recognise the contrast" between politics in Ireland and the UK.
He said the level of stability in the Dáil was helping Ireland cope with the threat of Brexit.
"That makes our country a much better place and puts our country in a much stronger position," he said.
The confidence and supply arrangement has already facilitated the passage of three budgets.
It ties Fianna Fáil to abstaining on votes of confidence in the Government or ministers, and when the Dáil votes on financial issues.
In return, the Government has agreed to consult the Opposition party on key budgetary decisions.
The original three-year deal was heavily focused on water charges.
Fianna Fáil has not sought any new spending or taxation commitments from Fine Gael in return for propping up the minority government, it has emerged.
Both parties have confirmed that the new arrangement is a basic extension to the 2016 deal which was heavily focused on the abolition of water charges.
Micheál Martin has this evening denied giving Leo Varadkar a blank cheque until spring 2020– but confirmed his own new demands relate to the passing of certain pieces of legislation.
He said the “easy decision” would have been to walk away and spark an election but he “looked at the horizon” and could only see the Brexit threat.
“It’s a very difficult decision. There are people that will not be happy within the party,” Mr Martin said.
Speaking to reporters at Leinster House, he said it would be “quite reckless” to add to the growing anxiety that people are feeling over Brexit.
“Brexit overshadows everything,” he said.
Tánaiste Simon Coveney was asked whether his party won a game of poker between the two parties but replied: “I’d like to think the country is the winner here.”
“I want to thank Fianna Fáil for the maturity of the decision taken today,” he said.
Mr Coveney noted the chaotic situation in the UK, saying it was good that the Irish political system could “respond when the country needs them”.
Asked whether Fine Gael could still be tempted to cause an early election, he said there was “no appetite” for an election.
Opposition parties reacted to news of the deal by suggest the past weeks of negotiations were meaningless and theatrical.
Sinn Féin leader Mary Lou McDonald was critical of Micheál Martin’s role in ensuring the government could continue for another year.
“It is now clear you have a Fine Gael/Fianna Fáil government in everything but name,” she said.
“Micheál Martin has been found out, he has acted with astonishing hypocrisy, he has delivered nothing and the people who will feel the brunt of it are the people out on the ground who we represent.
“I wouldn't have dared go back to our party leadership or membership with something as patently vacuous and empty as that. There hasn’t in fact been a negotiation, there has been a charade.”
Labour leader Brendan Howlin was also critical of the extension to the arrangement. He believes an election could have taken place early next year after the UK leaves the EU in March.
He said the deal amounts to “a blank cheque” being handed to the government.
“The six weeks of the labours of Hercules has delivered absolutely nothing. Apparently there is to be a deal with no consequences and no requirements. All the concerns about housing and health are meaningless because there are no new targets to be met.
“The Taoiseach is obviously looking for a mandate but he can’t bring himself to ask for that mandate.”
Meanwhile, insisting that the Government is prepared for a worst case scenario, Mr Varadkar told the Dáil today that the economy is “so strong, we’d continue to grow and not go into recession”.
However, he repeatedly sought to avoid direct questions on the plans in place to soften the blow of the UK crashing out of the EU next March.
More to follow