Mary Lou McDonald has confirmed that she will take part in RTÉ's Prime Time debate tomorrow night.
The Sinn Féin leader said she was "pleased" to accept an invitation from the broadcaster to appear beside Leo Varadkar and Micheál Martin.
The programme had initially been framed as a debate between the leaders of Fine Gael and Fianna Fáil.
In a statement, Sinn Féin's Director of Elections Pearse Doherty said Ms McDonald's inclusion "should not have come down to a last minute decision on the part of RTÉ".
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.
A spokesperson for the broadcaster said it had taken into account the Broadcasting Authority of Ireland's rules governing general election coverage.
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 three-way debate will take place on Prime Time on RTÉ One at 9.35pm tomorrow.
