Update 3.30pm: Micheál Martin has responded to Taoiseach Leo Varadkar's letter seeking an extension of the Government.
In his response issued this afternoon, Mr Martin said that the Taoiseach provided an "incomplete picture" of the ongoing implementation of the Confidence and Supply Arrangement.
"It is plain for all to see that there are still serious deficiencies, particularly regarding the emergency in Housing and the crisis in our Health service," Mr Martin wrote.
He reiterated Fianna Fáil's commitment to successfully negotiating the upcoming Budget.
The Confidence and Supply agreement ties the parties for three budgets and the review is set for after the conclusion of that budget.
"I don't see a reasonable basis for the statement in your letter that "government cannot function if it does not know if it will last from week to week or month to month".
"This has no grounding in our constitutional system and was not raised as an issue when the arrangement was negotiated.
"Indeed it would be extraordinary if we were to agree that Ministers could not be expected to do their jobs without advance assurance of a compliant Dáil."
Fianna Fáil has accused Taoiseach Leo Varadkar of causing political instability by sending out a distracting letter to Micheál Martin seeking an extension of the Government, writes Daniel McConnell.
The party's justice spokesman, Jim O'Callaghan, said the Taoiseach's letter appeared to be drafted for the benefit of the media rather than the good of the country.
He accused Mr Varadkar of trying to orchestrate an early election as early as October or November.
He said the Confidence and Supply agreement is crystal clear in that it ties the parties for three budgets and the review is set for after the conclusion of that budget and not before.
Mr O'Callaghan said it would be totally illogical to agree to a new deal ahead of budget talks being concluded.
Fianna Fail's Timmy Dooley says the Taoiseach should be focusing his efforts on issues like health and housing.
Mr Dooley said: "From my point of view, it would appear to be just a distraction away from the real issues, which is focusing on the Budget.
"The Taoiseach wants to talk about confidence and supply while we are just beginning a discussion about the Budget."
In his letter, Mr Varadkar said the budget is now less than six weeks away and said the Government cannot function or work in the interests of the people if it is living on borrowed time.
“A government cannot function if it does not know if it will last from week-to-week or month-to-month,” he said.
“Such uncertainty weakens our hand in Brexit talks, domestic negotiations and of course those opposed to reform are simply more likely to wait us out. Such a scenario would not be in the interests of citizens, taxpayers or users of our public services,” Mr Varadkar said.
“So, I am writing to you to seek confirmation that you are willing to re-commit to the Confidence and Supply Arrangement for the remainder of this Dáil. I suggest that in the interests of certainty, we agree a General Election date for the summer of 2020,” Mr Vardkar wrote.
Taoiseach Leo Varadkar is understood to have written to Fianna Fáil leader Micheál Martin with the aim of beginning talks on extending the Confidence and Supply Agreement for another two years, according to RTÉ.
Both parties are scheduled to meet tomorrow to discuss the Budget, which is five weeks away.
In recent days Micheál Martin has repeated that negotiations around the Confidence and Supply Agreement can only begin after the Budget.
Many senior figures in the party believe the deal could be extended by a year.
Fine Gael hopes to secure the deal for another two years to ensure stability.