Gardai were not involved in the bugging of the headquarters of the force's watchdog, it has been confirmed.
The Garda Siochana Ombudsman Commission (GSOC) revealed a security sweep of its offices last year identified three technical and electronic anomalies but said its databases were not compromised.
The watchdog released the findings after a meeting with Justice Minister Alan Shatter and calls from Taoiseach Enda Kenny to lay bare the extent of the breach.
GSOC said it did not report the bugging to the Government or call in gardai to investigate because no further action was needed.
"There was no evidence of Garda misconduct. The Commission decided to discontinue the investigation on the basis that no further action was necessary or reasonably practicable," it said in a statement.
"We did not wish to point fingers unnecessarily and we did not believe that widespread reporting would be conducive to public confidence.
"We took the decision not to report in good faith."
The watchdog said it regretted not revealing the security breach.
GSOC said it brought in UK experts to carry out a security sweep on the evenings of September 23-27 last year and follow-up investigations finished on December 17.
It said three technical and electronic anomalies were discovered that could not be conclusively explained and raised concerns about the integrity of its communications security.
"However GSOC is satisfied that its databases were not compromised," it said.
"Since the investigation concluded, we have been working to review and enhance our security systems in the light of what the investigation revealed."
Earlier Mr Kenny voiced concern after it emerged at the weekend the Garda watchdog last year hired a British security consultancy to investigate whether its headquarters in Abbey Street, and internal communications system, were being secretly monitored.
GSOC is responsible for receiving and dealing with all complaints made by members of the public concerning the conduct of members of the force.
Mr Kenny also questioned why the independent body had not informed Mr Shatter when it first became aware that espionage was suspected - noting that the office was law-bound to report unusual or exceptionally important matters to the minister.
"It is very important that the details of what transpired here be made available to the minister for public analysis and for reporting to the cabinet tomorrow," he said.
The Taoiseach told RTE: "I think it is important that we should understand on what grounds suspicions were determined in the first instance, who determined those suspicions, did the board discuss this and make arrangements for a company to assess whether or not interference in the communications system was had."
Mr Shatter met with commission chairman Simon O'Brien this afternoon, having asked for a report on the issue.
He is due to brief his cabinet colleagues on the episode tomorrow.
Earlier Communications Minister Pat Rabbitte described the claims as "sinister".
"Given the official role of the Garda Ombudsman and its supervision of the Garda Siochana, it is somewhat sinister if what transpired actually did happen," he said.
"But I don't think we should jump to conclusions until we get the report from the Minister of Justice."
Later, Garda Commissioner Martin Callinan reacted angrily over suggestions that the force had been suspected of bugging its oversight body.
The chief of police demanded the watchdog answer a series of questions over the controversy.
"It is a cause of grave concern that the Garda Siochana Ombudsman Commission's statement contains a clear indication that An Garda Siochana was in some way suspected of complicity in this matter despite Gsoc's overall finding that the existence of technical and electronic anomalies could not be conclusively explained," Mr Callinan said.
The Commissioner said he wanted Gsoc to clarify four things - the nature and extent of the anomalies identified and whether criminality is suspected.
Mr Callinan also called for an explanation on the basis for the suspicion of Garda misconduct.
And he also asked whether any matters identified need to be investigated by the Garda.