An official report into alleged bugging at the Garda Ombudsman headquarters has found no evidence of any surveillance taking place.

The report by retired High Court judge John Cooke says the evidence does not support the claim that the GSOC offices were under surveillance - and "much less" that Gardaí themselves were responsible.

Justice Cooke's report found that the presence of a British mobile phone network was probably as a result of a mobile phone company testing its new 4G network, which was connected to its main British IT systems.

While a so-called "ring-back" issue could not be explained, Justice Cooke finds no evidence of Garda involvement - and also that there was no evidence that a wireless device in GSOC's boardroom had actually been connecting to an outside WiFI network.

Justice minister Frances Fitzgerald says she has confidence in GSOC - but that Cooke's findings are clear:

The report admits that in the world of covert surveillance, it's extremely difficult to say for certain whether the security anomalies were the result of unlawful intrusion.

But Justice Cooke finds that in hindsight, GSOC's own internal investigation was not necessary - and that the suspicion of Garda involvement was influenced by GSOC's trouble in dealing with senior Gardaí.