The Smithwick Tribunal has heard that senior officers in the PSNI made a deliberate decision not to release crucial new intelligence to it for several years regarding garda involvement in the murder of two RUC officers.
One of the reports said a now retired garda did pass intelligence to the IRA, which led to the murder of two senior RUC officers in March 1989.
However, that garda is not one of the three being investigated by the tribunal.
The claim has emerged from intelligence reports gathered by the PSNI since the tribunal was set up.
Today a senior PSNI officer came to the tribunal to formally enter a summary of the reports before Judge Smithwick, but could not say why a decision was made not to release them before today.
Detective Chief Supt Roy McComb presented a summary of five intelligence reports that had been held by the PSNI.
They were all graded as reliable and accurate.
He said they had been collected by PSNI officers from sources since the tribunal was set up seven years ago.
He also confirmed that talks had taken place with the British Security Agency, MI5, before this intelligence was released to the tribunal.
The tribunal is investigating whether a garda passed information to the IRA, which assisted them in setting up the ambush that killed Chief Supt Harry Breen and Supt Bob Buchanan.
They had just left a meeting in Dundalk Garda Station just minutes before crossing the border and driving into the ambush in March 1989.
The tribunal has focused on three former garda sergeants, Det Sgt Owen Corrigan, Leo Colton and Finbarr Hickey. All three deny any suggestion they were involved in passing the information.
The first piece of intelligence said the IRA had received information from a garda "who had not been publicly associated at the Tribunal".
This individual had been paid a considerable amount of money for that information.
The second piece of intelligence stated that this garda had provided information in relation to Tom Oliver, a farmer from Cooley Peninsula who was abducted and murdered by the IRA because they believed he was passing information to the gardaí.
He also "continued to provide a variety of information to PIRA for a number of years. It is believed that this officer is now retired. He was handled as a source by a senior member of PIRA".
Separate intelligence reports indicated that a garda provided information to the IRA, which led to the murder of the two RUC officers.
The final summary presented to the tribunal today stated that a former detective garda in Dundalk, Jim Lane, said that other officers Corrigan, Colton and Hickey, had "unethical relationships with PIRA members".
Under cross-examination, the Det Chief Supt Roy McComb accepted that Mr Lane said the opposite when he was giving direct evidence to the tribunal.
In answer to further questions from Michael Durack, senior counsel for the Garda Commissioner, the witness said these intelligence reports came in since the tribunal was established seven years ago.
He said a decision was made not to release them but that had now changed. He said he did not have the information who made the decision not to release the reports originally.
Counsel for Mr Corrigan, Jim O'Callaghan, put it to Det Chief Supt Roy McComb that while the PSNI did release one intelligence document, which identified his client as a source of information to the IRA, these documents, which showed the exact opposite, were hidden for several years.
The witness accepted that Mr Corrigan was not named in the intelligence reports.
Mr O'Callaghan said the PSNI has had this information for up to seven years suggesting that someone else was involved in setting up these two RUC men and they did not provide that to the tribunal until today when it was drawing to a close.
Det Chief Supt Roy McComb said the intelligence reports were available but he did not know who made the decision not to release them.
"What the PSNI did was hang Mr Corrigan out to dry," said Mr O'Callaghan.
Det Chief Supt McComb was also questioned by Neil Rafferty, counsel for Peter Keeley, who worked as an agent in the IRA for the British security services.
On a previous occasion before the tribunal, the PSNI officer said there were concerns among republicans about what the tribunal was looking at and that deliberately false testimony had been given from the witness box.
Today he accepted that misinformation by the IRA, which would end up before the tribunal, was "a reasonable risk".
Intelligence is an imprecise art, according to Det Chief Supt McComb.
Mr Corrigan resumed his evidence today and was cross-examined by Mr Rafferty.
Mr Keeley had claimed he was present when Mr Corrigan passed information to the IRA.
However, Mr Corrigan has strongly disagreed with the claims.
Today he said he did not know senior IRA figures Patrick 'Mooch' Blair and Patsy O'Callaghan.
He also said he had volunteered to go to the Falls Road in Belfast at the request of the Irish government to act as an observer.
Mr Rafferty responded that the only volunteer Mr Corrigan was was a volunteer for the IRA.
A report entitled HMG 151 was also discussed briefly at the tribunal today.
It was a letter written to the Secretary of State for Northern Ireland by an official in the Northern Ireland Office outlining a meeting with the Ulster Unionist Party.
At that meeting it had been claimed that a senior Catholic RUC officer was the source of the leak about the visit of Chief Supt Breen and Supt Buchanan to Dundalk.
Speaking afterwards, the families of the two RUC men both expressed concern at what had emerged in the Tribunal today.
Ernie Waterworth for the family of Supt Buchanan, said they were "deeply disappointed" that information such as the PSNI intelligence was only emerging so late in the day.
It posed the question of what other material the PSNI holds but has not released, he said.
Both he and John McBurney for the family of Chief Supt Breen said the issue of a possible leak from a fellow RUC officer was of serious concern.
Mr McBurney said there was now "a bewildering and alarming array of collusion pointers" and urgent work was needed to "unravel the tangled strands now exposed".
