Garda Commissioner Martin Callinan has strongly rejected claims of collusion by a member of his force with the IRA that led to the murders of two senior PSNI officers twenty four years ago.
He also accused the PSNI of failing to co-operate fully with the Smithwick tribunal, which was set up to examine the collusion allegations.
For the past eight years the tribunal has been investigating the claims that the officers, Chief Supt Harry Breen and Supt Bob Buchanan were murdered by the Provisional IRA as they were returning from a visit to Dundalk garda station, because of a garda tip off.
The murders were carried out on March 20, 1989.
At the final day of public hearings, counsel for the Garda Commissioner, Mr Diarmaid McGuinness, dismissed the allegations as not merely nonsense but "nonsense on stilts".
He said three formers of the garda force, Owen Corrigan, Leo Colton and Finbarr Hickey had at differen stages of the tribunal been described as the source of a tip off to the IRA that led to the fatal ambush of the then RUC officers.
But towards the end of the tribunal new evidence was given by PSNI assistant chief constable, Drew Harris, that the IRA informant was neither of the three but either an unknown female at Dundalk garda station who made a phone call to an unknown member of the IRA or else an unidentified administrator somewhere in the Republic.
Mr McGuinness said the tribunal had not been give the full details of that intelligence or when it had been received.
There was no evidence to back up the statement by the assistant chief constable that this intelligence was reliable.
He accused the PSNI of failing to co-operate with the Garda Siochana after earlier stating they would share the intelligence with them as well as failing the Breen and Buchanan families and failing the tribunal.
And he said it was the submission of the garda that there was nothing to support the claims that collusion leading up to the murders ever existed.