Northern Ireland's Deputy First Minister Martin McGuinness has offered to testify at a tribunal where it was claimed he was involved in the IRA sanctioning the murders of two RUC officers.
But the Sinn Fein MP insisted he would have nothing to contribute to the Smithwick inquiry in Dublin because he has no knowledge of the incident.
Mr McGuinness said: "I made it clear some time ago if there was a need for me to (attend), I would be prepared.
"But I thought I had absolutely no contribution to make whatsoever. It's an incident I know absolutely nothing about."
British intelligence officer Ian Hurst - also known as Martin Ingram - claimed at the inquiry to have inside knowledge linking the Sinn Fein chief to an order for the 1989 border ambush of Chief Superintendent Harry Breen and Superintendent Bob Buchanan.
Mr McGuinness dismissed the evidence against him read into the record at the tribunal as nothing more than "a yarn".
"I've totally and absolutely refuted and rejected what turned out to be a yarn, a cock-and-bull story given to the Smithwick Tribunal by a man initially named as Hurst."
He described the witness as a fantasist.
The inquiry into IRA-garda collusion was told Mr McGuinness was in the IRA's northern command and "involved" when terror chiefs sanctioned the double murders on their way home from a cross-border policing briefing.
Ingram, as he was known outside intelligence circles, told the inquiry that intelligence on the Buchanan and Breen atrocity came from the high-level double agent in the IRA known as Stakeknife, allegedly notorious Belfast republican Freddie Scappaticci.