GARDA Commissioner Noirín O'Sullivan has denied spreading allegations of sex crimes against a whistleblower in the force.
The police chief said she was surprised by claims of her involvement in a smear campaign targeting Sergeant Maurice McCabe and insisted it was the first time she had heard the accusation.
The explosive allegations about a sex crime slur were revealed by Labour leader Brendan Howlin who said he was contacted by a journalist who claimed to have direct knowledge of the commissioner being in contact with other reporters.
Ms O'Sullivan said she was taking an unprecedented step to publicly deny the claims despite a judge-led inquiry being ordered.
A statement from her office said: "The commissioner has no knowledge of the matters referred to by Deputy Howlin and refutes in the strongest terms the suggestion that she has engaged in the conduct alleged against a serving member of An Garda Síochána.
"This is the first occasion on which the commissioner has been made aware of the allegations made by Deputy Howlin and to her knowledge no report having been made to the Garda Síochána Ombudsman or elsewhere relating to the specific allegations."
Judge Peter Charleton has been appointed to lead an inquiry into allegations that senior officers attempted to blacken Sgt McCabe's name among the media with unfounded allegations.
He will examine nine issues including whether Commissioner O'Sullivan knew about it or if she played any part in directing it.
The commissioner said Judge Charleton will get full cooperation from the force.
"In the interim, the members of An Garda Síochána affected by the remarks published yesterday will receive all necessary supports and assistance having regard to the potential impact for the members concerned and their families," the commissioner's statement read.
The smear campaign allegations were made by the former head of the Garda press office, Superintendent Dave Taylor, who is suspended from the force over the leaking of the names of Roma children taken into social care in 2013.
Mr Taylor claimed that senior gardai targeted Sgt McCabe in a widespread character assassination by passing on false and damaging allegations.
The decision to call a full judge-led Commission of Inquiry was taken following a recommendation by Judge Iarfhlaith O'Neill, who filed a report on the scandal to tanaiste and justice minister Frances Fitzgerald last December.
Under Dáil privilege, Mr Howlin said a journalist told him that Commissioner O'Sullivan called journalists during 2013 and 2014 about "very serious allegations of sexual crimes having been committed by Garda Maurice McCabe".
"The journalist to whom I spoke this morning is somebody I know, and who I believe has the utmost integrity," Mr Howlin said.
"That journalist has not received direct contact from Commissioner O'Sullivan, but has direct knowledge of such contacts with other journalists.
"I am satisfied that the allegations raised with me this morning were of sufficient gravity that they deserve to be considered in full, and that they underline the need for Commissioner O'Sullivan to stand aside from her duties while the commission of investigation is under way."
Mr Howlin said the commissioner's position was untenable as she would be required to hand over phone records held under her authority by the force.
The Labour leader said the allegations date from a two-year period around the time when a separate internal inquiry was launched over the leaking of information to the media by another senior officer.
Taoiseach Enda Kenny said the allegations were "of the most serious import" and "wholly and vehemently denied".
Mr Kenny rejected the call for Ms O'Sullivan to stand aside as commissioner and no finding of wrongdoing had been made against her.
Ceann Comhairle Seán Ó Fearghaíl criticised Mr Howlin for repeating allegations in the Dáil against someone who cannot defend their reputation in the parliament and said the claims were "extremely dangerous".
