Sinn Féin leader Mary Lou McDonald has confirmed that she will participate in RTÉ's Prime Time debate tomorrow night.
The broadcaster said this afternoon that she has been asked to join the leader of Fine Gael, Leo Varadkar, and Fianna Fáil's Micheál Martin.
The decision, which comes just five days before polling day, was made following a meeting of the RTÉ Election Steering Group today.
Ms McDonald has since confirmed that she will take part in the debate.
In a statement, Sinn Féin's Director of Elections Pearse Doherty said he was "happy" to confirm the party leader's participation, but added that "this should not have come down to a last minute decision on the part of RTÉ".
He said: "Fine Gael and Fianna Fáil wanted this election to be about them, but this election was never about two parties with no real policy differences, who have effectively been in government together for the last four years. Neither of them represent change."
The programme had initially been framed as a leaders' debate between the heads of the country's two largest political parties.
RTÉ also said it will invite the leaders of five other parties to a debate on Prime Time on Thursday night.
It follows a seven-way debate between all party leaders on Claire Byrne Live last week.
'Change in the dynamic of the campaign'
A spokesperson for the broadcaster said it had taken into account the Broadcasting Authority of Ireland's rules governing general election coverage.
In particular, it noted rule 27 which provides that broadcasters should "give active consideration to their approach to coverage over the duration of a campaign and amend this approach if they consider it necessary and appropriate so as to ensure fairness, objectivity and impartiality."
"Broadcasters are encouraged to seek out the widest range of opinions on the issues raised during any given election."
In a statement, they said: "RTÉ is very mindful it has a duty to the public to reflect events as they unfold.
"During the course of the campaign and over recent days RTÉ has taken into consideration the notable change in the dynamic of the campaign on the ground, and representation and statements by political parties.
"The dynamic has also been consistently reflected in all opinion polls since the campaign commenced."
RTÉ said it felt it was necessary to amend its initial approach with regards to the debate and to "continue to put the audience first".
The invitation to include the Sinn Féin leader comes after an opinion poll released yesterday revealed that the party is neck and neck with Fianna Fáil to win the General Election.
The Red C poll for the Business Post had Sinn Féin up five points to 24% support - tied with Fianna Fáil and three ahead of Fine Gael.
Overall, Mary Lou McDonald's party has seen its support jump 13% in Red C polls since November.
On Saturday, a survey released by The Times Ireland and Panelbase found that Sinn Féin had overtaken Fine Gael to become the second most popular party.