Judge Peter Smithwick has unleashed a blistering attack on the Garda - accusing it of prizing loyalty over honesty.
The tribunal chairman said he was depressed and disheartened that a culture still exists in the force where its reputation takes priority over everything else.
"Loyalty is prized above honesty," he said.
In his report, Judge Smithwick takes on the Garda Commissioner, whose lawyers he accused of setting out to undermine former chief superintendent Tom Curran.
Describing Mr Curran as of the utmost integrity, the tribunal fully accepted evidence from the former Monaghan police boss that he told Garda HQ in 1988 that Superintendent Bob Buchanan was on an IRA hit list.
The intelligence, from an informant, was passed to then assistant commissioner Eugene Crowley but there are no records or files to show the information was acted upon.
Shockingly, Judge Smithwick states Mr Buchanan and Chief Superintendent Harry Breen might not have been murdered if Garda HQ had warned their counterparts in Northern Ireland about the intelligence.
"Had this been done, the life of Superintendent Buchanan, and consequently that of Chief Superintendent Breen, may have been saved," he said.
Furthermore, there are no files in Garda HQ about intelligence handed over by Mr Curran suggesting former Dundalk-based detective sergeant Owen Corrigan was "inappropriately associating" with the IRA.
The lack of records were branded a "serious concern" in the report.
Mr Curran testified that although he knew Mr Buchanan, he did not warn him personally about the threat to his life because he believed higher authorities were best placed to assess the risk and act accordingly.
Judge Smithwick said the Garda Commissioner's lawyers set out to cast doubt over Mr Curran's credibility "on the basis that the Garda Commissioner did not like what Mr Curran had to say."
The tribunal chairman said the legal team were there to protect all ranks of the force, but they did not give any advice or protection to Mr Curran.
"I would have thought he is as deserving of the support of the Garda Commissioner as any other former officer," he states.
"However, it seems to me that because he was giving evidence of which An Garda Siochana did not approve, such support was not forthcoming."
In an outspoken attack on the force, he concludes that the Garda prioritises "the protection of the good name of the force over the protection of those who seek to tell the truth".
Judge Smithwick said it was "disheartening and depressing" that such a culture remained within the force two decades after suggestions emerged of collusion between the force and the IRA.
There have been three Garda commissioners during the course of the Smithwick Tribunal, including the current chief Martin Callinan and his predecessors Fachtna Murphy and Noel Conroy.