Sinn Féin leader Mary Lou McDonald has been invited by RTÉ to take part in tomorrow night's Prime Time leaders' debate.
The debate was to be between Fianna Fáil leader Micheal Martin and Fine Gael leader Leo Varadkar.
But RTÉ's General Election steering committee met today to consider representations from Sinn Féin for Ms McDonald to take part in the debate.
Sinn Féin director of elections Pearse Doherty welcomed the decision by RTÉ and confirmed that Ms McDonald will accept the invitation.
He said: "I want to welcome the decision by RTÉ to extend an invite to Mary Lou McDonald to take part in tomorrow's party leaders' debate on Prime Time, and I am happy to confirm that Mary Lou will be participating.
"That being said, this should not have come down to a last-minute decision on the part of RTÉ.
Meanwhile, Fianna Féil and Fine Gael have criticised Sinn Féin's tax pledges as "fantasy policies", claiming they will hurt ordinary workers.
Paschal Donohoe said Fine Gael will seek to emphasise with voters that not all change is good, as recent polls showed a drop in support for the party.
The Republic of Ireland's General Election campaign has entered its final week, with all parties and independent candidates preparing to make their final pitches to voters.
Speaking in Dublin on Monday, Mr Donohoe said: "Not all change can be risk-free and not all change can be positive.
"What we are going to be doing as we head into the final week of the campaign is emphasising that in our manifesto and in the plans that we have published we have recognised the progress that has been made in our country - due to the sacrifices of the Irish people - and making the claim to the Irish people that change is happening and we are ambitious for more change to happen."
He added: "In relation to Fianna Féil and they changes they say they will make - where are their plans? Where is their detail?
"We will be building on what we have already done, acknowledging what needs to be done and be unapologetic in challenging other parties that are putting forward mantras of change but in offering these mantras of change.
"Fianna Féil are putting forward their worst hits of their recent past and what Sinn Féin are offering is the kind of ideas that will do such harm to workers income, to wages and to their jobs."
"They have claimed they are going to put forward new ideas for investment involving 15 different tax hikes - tax hikes that would be bad for those at work, tax hikes that would be bad for those looking to create jobs."
Fianna Féil finance spokesman Michael McGrath claimed Sinn Fein's tax policies will leave Ireland a "cold place" for businesses.
Among its pledges, Sinn Féin said it plans to abolish the Universal Social Charge on the first 30,000 euro earned and to abolish the property tax.
Outlining Fianna Féil's strategy for the final campaigning days, Mr McGrath used the opportunity to hit out at Sinn Féin, who tied first place with the party in a recent opinion poll.
"These policies are fantasy policies that will not add up in the real world," he said.
"In the real world, people change their behaviour, they make investment decisions depending on the change in taxation and enterprise landscape in the country.
"Sinn Féin want to make this a very cold place for business. They want to tax employment through increasing PRSI (Pay Related Social Insurance), they want to tax people over 100,000 euro under the pretence that won't affect anybody below 100,000 euro."
Speaking at their election headquarters in Dublin, Mr McGrath also claimed Sinn Féin's tax policies will "boomerang back into the face of the very people that they are saying they're going to help".
Micheal Martin was pressed on his party's position on going into government with Sinn Féin after a number of his TDs and candidates indicated they would be open to working with Mary Lou McDonald's party.
"It's not just about the past but about the future as well," Mr Martin told RTÉ.
"I was in Killarney yesterday, thriving in tourism, Sinn Fein tax proposals would destroy the enterprise that was so evident and has made Killarney what it is in terms of employers.
"Do not underestimate the strength of will within the Fianna Féil party who have all rejected the prospect of a Fianna Fáil-Sinn Féin coalition."
The Fianna Fáil leader also said he has "no issue" with Ms McDonald taking part in the final televised leaders' debate.
Asked about Leo Varadkar's comments that Fianna Fáil has "a lot of backwoodsmen", Mr Martin said it was beneath the office of An Taoiseach.
Mr Varadkar kicked off his final week of campaigning saying he will work until the final moments to convince people to vote for Fine Gael.
He raised concerns over other parties' pledges to reduce the pension age back to 65.
"I appreciate what we're offering is less than what the other parties are offering on this but I'm concerned that what's happening is an auction and an auction that could result in us auctioning off the pensions of the young," he said.
Acknowledging Fine Gael is behind in the opinion polls, he claimed they are only a "snapshot in time".
He added: "There have been a lot of comments about me in this campaign from various different angles and I don't believe that this election campaign is about me.
"I believe it's about 4.5 million citizens of Ireland."