Fianna Fáil's Jack Chambers has insisted Fianna Fáil will "absolutely not" enter into a coalition government with Sinn Féin after the General Election.
He said when there is a complete incompatibility between two political parties, "there is no room for negotiation, there is no common ground".
Party leader Micheál Martin said the parties had serious differences in their economic plans, and this is clear from their manifestos.
Asked if Fianna Fáil would enter into a coalition with Sinn Féin if it was what the numbers dictated after the election, Mr Chambers said it is not about numbers, "it's about principles on the economy, it's about policy".
Sinn Féin leader Mary Lou McDonald accused Fianna Fáil leader Micheál Martin of being "absolutely determined" to put Fine Gael back into Government.
She rejected accusations that her party was not pro-Europe or pro-enterprise.
In the General Election, and with just three days of campaigning left, three parties are publishing policies on the cost of living, with two others focused on climate action.
Fianna Fáil leader Micheál Martin was in the Dublin South Central constituency, with Senator Catherine Ardagh, before preparing for tonight's leaders debate on RTÉ.
He said he was "looking forward" to the debate and thought there will be "a lot of public interest" in it.
The party's Dublin West candidate Jack Chambers, along with Dublin Central candidate Mary Fitzpatrick, set out the party's priorities to safeguard our economy from international shocks and outline cost of living measures to support families, workers and businesses.
Sinn Féin leader Mary Lou McDonald campaigned in Dublin South Central with her party's three candidates - Aengus Ó Snodaigh, Cllr Máire Devine and Cllr Daithí Doolan.
She said she was feeling "good" ahead of the debate.
"I want to strike a note of hope, a note of optimism, a note of purpose, but also a note of challenge", she said.
Sinn Féin's Pearse Doherty, Louise O'Reilly and Eoin Ó Broin set out their party's plans to deliver long-term reductions in the cost of living for workers and families.
Fine Gael leader Simon Harris did a series of five regional radio interviews, before preparing for the leader's debate.
Fine Gael's Paschal Donohoe emphasised the "huge value" of having "economic stability" and a "stable government", three days before the general election on Friday.
He said "in order to help" address issues such as housing and cost of living "we need economic stability and stable government".
And, Mr Donohoe said, he wants to "ask the Irish people in the last few days" of the election campaign to "consider that stability" as we are "in a world of continuing change".
Labour Party Fingal East candidate Duncan Smith and Fingal West candidate Cllr Rob O'Donoghue unveiled their party's plans on how to decarbonise Ireland's transport system and invest in reliable public transport and active travel.
The party said the completion of the MetroLink was a key part of its transport policy.
"It has to be delivered and it's a red line for us as a party. I say it's not just a priority, it's a flagship policy for the Labour Party," said Mr Smith. "I don't think we could go back to the people in this constituency if MetroLink gets planning permission and not to have it started and well progressed in the course of the next government."
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Green Party leader Roderic O'Gorman outlined his party's climate action credentials at an event in Dublin.
He said that the Green Party delivered "the lowest emissions for 30 years last year, falling by 7% at the same time the economy is growing".
"Our manifesto sets out clearly how we will achieve the major transformation that is needed over the next five years so we can complete the project we started in 2020," he said.
Social Democrats held two policy launches.
Gary Gannon of Dublin Central, Eoin Ó Broin of Dublin Mid-West and Sinéad Gibney of Dublin Rathdown outlined the party's cost of living measures.
Mr Gannon said the party was very clear that they wanted to be in government and that the three leaders in tonight's debate must be asked which of them will commit to a senior minister for disabilities.
"You cannot go into government if you cannot get your purpose onto the agenda. For us we have five dealbreakers and we will strongly negotiate for all. Those things are how we will change society. There is no point in us being in government to make up the numbers. We want to be in government to change the fabric of this society," he said.
Cork South-Central candidate Cllr Pádraig Rice, along with outgoing deputy and former leader Catherine Murphy, launched the party’s workers’ rights policy in Cork.
People Before Profit's Dublin North-West candidate Cllr Conor Reddy launched his party's youth manifesto today in Trinity College Dublin, along with leader Richard Boyd Barrett and Meath East candidate Clara McCormack.
The policy is entitled: "No Country for Young People".
Meanwhile, the Independents 4 Change candidate in Dublin Central, Clare Daly, is due to outline vision for the constituency, and beyond this afternoon.
She is due to be joined by former Independent Dublin Central TD Maureen O’Sullivan and civil rights campaigner Bernadette McAliskey.
More than 400,000 voters added to register
Since January, when An Coimisiún Toghcháin began encouraging people to register, 423,000 new voters were added, while 220,000 amended their details.
In the last fortnight before the deadline for registering closed on 12 November, 100,000 new voters registered to vote.
Updated figures from An Coimisiún Toghcháin show that 3,681,543 people are registered to cast a ballot in Friday's General Election.
Additional reporting Evelyn O'Rourke, Tommy Meskill, Fiachra Ó Cionnaith, Fergal O'Brien, Joe Mag Raollaigh
