State-run broadcaster RTÉ has been forced to include Sinn Féin leader Mary Lou McDonald in a final televised leaders’ election debate as its historic surge in polls continues.

Sinn Féin has confirmed that Mary Lou McDonald will accept the invitation. Elections in the Republic of Ireland are scheduled for Saturday 8 February.

Sinn Féin is now the joint most popular party state at 24% support, alongside Fianna Fail but ahead of Fine Gael, who are now on 21%, according to the latest Red C poll. Other polls have shown a similarly large increase in Sinn Féin’s vote share.

RTÉ announced its decision to reverse its position and invited Ms McDonald to participate in Tuesday evening’s debate.

The debate was scheduled to be only between Taoiseach Leo Varadkar and his confidence-and-supply partner Fianna Fáil leader Micheál Martin, with Sinn Féin’s requests for Ms McDonald’s inclusion repeatedly rebuffed.

The public pressure to include Ms McDonald had become a major embarrassment for RTÉ, whose position was made increasingly untenable by the polls.

The wave of public support for change has caught all sides by surprise, and the polls show it is falling overwhelmingly to Sinn Féin. They have have caused panic in the ranks of Fianna Fail and especially for Fine Gael, whose support continues to plummet.

Support for Sinn Féin has vaulted most in the age groups up to 54, a huge transition in those middle-aged demographic categories who are among the most likely to vote.