Fianna Fáil leader Micheál Martin has said that Taoiseach Leo Varadkar told him last week that he could not be sure of support from his own party.
Mr Martin said that during their discussions last Thursday Mr Varadkar also said he was not sure whether all Fine Gael TDs would support his Government in Dáil votes.
His comments came as opposition parties gear up for a February general election after Mr Varadkar said yesterday that he had "made a decision" on the date and would clarify matters shortly.
Speaking on RTÉ's Today with Sean O'Rourke, Mr Martin said his party had been a very responsible fiscal opposition party and had facilitated responsible budgeting over the last five years.
However, he said the Government had failed on health and housing.
He accused the Government of being too fixated with its image to focus on these important issues and said that no one bought the argument that "good times are here again".
Mr Martin said there had been a distinct failure in housing and the homelessness numbers were a sign of this failure.
He said he believed Fianna Fáil would do well in the next election and had a strong team to stand election.
He also reiterated that his party would not enter coalition with Sinn Féin because he does not trust the party.
The Minister for Employment Affairs and Social questioned how Fianna Fáil could be trusted to manage the economy if it had not learned the lessons from the past.
Speaking on the same programme, Regina Doherty said Mr Martin still cannot take responsibility for the economic crash.
Ms Doherty said economic improvements under Fine Gael have allowed for investment in healthcare, transport, education and social protection.
She also said she did not think a coalition between Fine Gael and Sinn Féin would work due to an inability to build consensus.
Sinn Féin leader Mary Lou McDonald said she has "made it clear" that after the next election she will talk to and listen to everybody "because that's what adults do".
She said she was not surprised that Mr Varadkar and Mr Martin "do not want Sinn Féin about the place" because "they know full well that we will bring about change".
Ms McDonald said that if Sinn Féin is capable of governing with the DUP in Northern Ireland, then it was capable of governing with parties in the Republic.
"If Sinn Féin can govern in partnership with the DUP - people we have profound political differences with - how on earth is it logical to then say that Sinn Féin isn't good enough to be in government in the south?"
Ms McDonald said that if we can "land at a space where we have a republican programme for government" then Sinn Féin will "be in the business of entering government".
In yesterday's interview on RTÉ's This Week, Mr Varadkar was asked about an upcoming no-confidence motion in Minister for Health Simon Harris, given his Government's reduced working majority in the Dáil.
He replied that "a Taoiseach that can't appoint their own Cabinet is a Taoiseach in name only".
This effectively confirmed that his minority administration is no longer confident that it can command the necessary votes.
The architect of that motion, Independent TD Michael Collins, said he has the required numbers to put a vote, but it appeared the Taoiseach was pulling the plug on the Dáil before that could happen.
Labour leader Brendan Howlin said the Taoiseach had effectively fired the starting gun of the campaign.
He said his party would campaign on ending waste and investing in public services.
Mr Howlin also said he expects Labour to have a "surprisingly positive election".
Speaking on RTÉ's Drivetime, the Wexford TD said that when he assumed the party leadership he stated his intention to double the number of Labour TDs from the seven elected at the last election.
Mr Howlin said that while Willie Penrose and Brendan Ryan are not standing for re-election in Longford/Westmeath and Dublin Fingal respectively, he expects Labour candidates to hold both seats.
Kevin Boxer Moran tells RTÉ News he remains part of the Independent Alliance until Government falls. He will then stand as an Independent not linked to the Alliance but is open to being part of a similar alliance in next Dáil if he's re-elected. @rtenews— Mícheál Lehane (@MichealLehane) January 13, 2020
Meanwhile, Minister of State Kevin 'Boxer' Moran has confirmed that he will cut his ties with the Independent Alliance grouping once the election is called in the coming days.
He said he intends to stand as an unaligned Independent candidate.
Elsewhere, Dr Michael Harty, who is an Independent TD for Clare, has announced that he will not contest the upcoming election for personal and professional reasons.
Reporting Paul Cunningham, Micheál Lehane