Garda informants could be "killed on the streets" if confidential details about their identities are leaked.
The warning was issued yesterday by Garda Commissioner Martin Callinan to highlight the need for secrecy and sensitivity in dealing with the informants.
He made it clear that no informant was run by a garda agent "off the book" and said there were strict guidelines governing the handling of each informant.
Mr Callinan also pointed out that "participating" agents – where the person was taking an active part in a crime – were not a feature in this country.
If such a scenario arose, the issue must be referred to the Director of Public Prosecutions, he added, but informants were not given carte blanche to commit crime.
He rejected suggestions that the gardai had not co-operated fully with the Garda Ombudsman Commission during its investigation into the Kieran Boylan drugs case.
Last week a furious row broke out between the gardai and their watchdog, the Garda Siochana Ombudsman Commission (GSOC), over the results of a four-year investigation into alleged collusion between senior officers and Boylan, a convicted drug trafficker from Ardee, Co Louth.
Justice Minister Alan Shatter published a judge's report which found gardai were in compliance with guidelines.
The DPP had already found no evidence of wrongdoing, after it examined a file provided by GSOC. And GSOC also conceded that it does not intend to pursue any disciplinary action against the detectives in question.
Mr Callinan agreed that the ombudsman was fully entitled to all of the information it sought but he was obliged to seek assurances to protect the identity of all informants.
He said both sides had clear statutory roles and the issue being sorted out if they were to do business was the steps being taken to avoid that problem arising.
"We have a clear duty of care to the people involved", he added.
He told Dail public accounts committee member John Deasy that it was extraordinarily difficult for the agents and they had to walk a very thin line.