Sinn Féin leader Mary Lou McDonald has accepted an invitation to take part in tomorrow's Prime Time leaders' debate.

Originally, the debate was to be held between the Fine Gael leader Leo Varadkar and the Fianna Fáil leader Micheál Martin.

However, this afternoon an invitation was sent to Ms McDonald following a meeting of RTÉ's General Election steering committee.

RTÉ's Managing Director of News and Current Affairs Jon Williams said the dynamic nature of elections had been taken into account by the station's steering committee in arriving at its decision.

Sinn Féin's director of elections Pearse Doherty welcomed the decision by RTÉ to extend an invite to Ms McDonald.

He added that it "should not have come down to a last minute decision on the part of RTÉ".

Yesterday, Mr Doherty had argued that recent opinion polls proved that the criteria used to exclude Ms McDonald were redundant.

In a statement today, RTÉ 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.

"We now consider it necessary to amend our original approach, respond to the changes in the campaign, and continue to put the audience first in the making of Tuesday night's programme."

In addition, RTÉ has also decided it will invite the leaders of five other parties to a debate on Prime Time on RTÉ One this Thursday night.

Both Mr Varadkar and Mr Martin said yesterday that while it was up to RTÉ to decide who should participate in any debate, they did not have any difficulties if the format was changed to accommodate Ms McDonald.

This evening, Mr Varadkar welcomed the decision to include Ms McDonald in the debate.

Speaking in Limerick, the Fine Gael leader said it would provide an opportunity to scrutinise the party's policies.