The Taoiseach has told the Dáil that Tánaiste Frances Fitzgerald "had no prior knowledge" of a strategy pursued by former garda commissioner Nóirín O'Sullivan's legal team to attack the credibility of Sgt Maurice McCabe during his testimony before the O'Higgins Commission.

Leo Varadkar said Ms Fitzgerald had "no hand, act, or part in the strategy, and only found out about it after the fact".

He said the position was the same for the current Minister for Justice Charlie Flanagan.

Fianna Fáil leader Micheál Martin said there was "genuine shock" when it emerged that the commissioner's legal representatives had been instructed to attack the motivation and integrity of Sgt McCabe. 

"That was not how it was meant to be, it was about finding out the facts, it was never meant to be an attack," he said.

Mr Martin said there were various reports in the public domain about a phone call to the Department of Justice in relation to this strategy.

He said legitimate questions had been raised by Labour TD Alan Kelly, "questions which should have got straight forward answers" he said.

"Did the Tánaiste know about the attack on the credibility of Sgt McCabe at the time?" he asked.

In response, Mr Varadkar said he spoke to the Tánaiste, who was currently on Government business in the United Arab Emirates.

"She confirmed that she had no hand act or part in forming the commissioner’s legal strategy, nor did she have any prior knowledge of it," Mr Varadkar responded.

He said she did find out about it after the fact, around the same time as everyone else.

The Taoiseach said the Department of Justice had not been able to find any record of being informed before the fact about the strategy the commissioner was going to pursue.