A senior Garda officer has said it is "totally and utterly untrue" that he was told of allegations that confidential conversations between prisoners and solicitors were secretly recorded during the investigation into the death of Raphoe cattle-dealer Richie Barron in 1996.
John White, a former detective-sergeant, has alleged that he told Chief Supt Austin McNally of the allegations at a meeting in a Sligo hotel in November 1999.
Mr White says the officer said the bugging of interview rooms was "one of the best-kept secrets" in the Garda Síochána.
"That is totally and utterly untrue. He never mentioned anything about recordings," said Chief Supt McNally, who is currently with the Bureau of Fraud Investigation.
Chief Supt McNally said that the meeting was held to discuss the movements of two Raphoe gardaí, John O'Dowd and Padraig Mulligan, the night Mr Barron died, and that Mr White told him the two men were in a pub that night.
The officer said Mr White used "colourful language" to make his allegations sound true and had used "the occasion of a legitimate encounter to put his own spin on things". He said he had "absolutely no experience and no knowledge" of secret recording of prisoners' conversations in his Garda career.
"If what Mr White is alleging is correct, to think that I, as a senior officer with 26 years' service, would suddenly turn round and sacrifice my principles that I worked for for so long to engage in this nefarious activity, he is very wrong," he said. "And I consider it a terrible slur on all the good people I have served with over the last 40 years."
Mr White also said he had met Chief Supt McNally and Assistant Commissioner Kevin Carty in June 1995 to give them information on a drugs-related murder case in Dublin, and that he and other senior officers were now trying to distance themselves from him.
Chief Supt McNally said he had no recollection of meeting Mr White during the investigation. He said that when allegations of bugging in Garda stations first emerged in an article in the Donegal Democrat he "knew it was utterly false, utterly false".
"I am saying it never happened on oath," he told the chairman.
The tribunal is examining allegations by the former sergeant that privileged conversations were covertly recorded.