The Garda Siochana Ombudsman Commission (Gsoc), which investigates complaints made against Garda members, has found evidence that its discussions, telephone calls and emails had been hacked by an unidentified source.

The discovery was made last year when the organisation carried out a sweep of its offices using a UK-based private contractor that specialises in counter surveillance.

Since then, security has been improved in Gsoc including the establishment of a dedicated meeting room that cannot be bugged.

The sweep of Gsoc’s offices in Middle Abbey St in Dublin’s north inner city found a speaker phone in a conference room where cases were discussed was bugged.

There was no physical bugging device in the phone, though a check on the line revealed it had been electronically monitored in a way that enabled a third party to listen in to conversations being conducted in the room and on the phone in question.

The UK security consultants that carried out the inspection on behalf of Gsoc also concluded that the office’s wi-fi system had been compromised from outside the building.

This form of bugging would enable those responsible to intercept any emails sent over the system, including those containing sensitive information relating to Gsoc’s cases and confidential reports compiled as part of its work.

It was also revealed that a second wi-fi system had been used to similarly access material sent and stored electronically by Gsoc staff. That wi-fi led investigators to an internet protocol (IP) address in the UK.

However, it was not possible to pinpoint its exact location or to establish the identity of those behind the address.

The investigation also concluded that another electronic device used to store material by the Garda complaints watchdog had been accessed via convert surveillance. However, when those behind the surveillance became aware that their activities had been detected, they immediately erased data.

The decision to bring in experts from the UK to check its systems was made when Gsoc consulted with its equivalent organisation in the UK, the British Independent Police Commission.

Gsoc has declined to comment on the case and this afternoon Minister for Justice Alan Shatter, under whose justice remit Gsoc falls, had made no comment.

The details of the case first emerged in a news report in The Sunday Times newspaper today.

It is understood because Gsoc was unable to determine when the surveillance had begun, how long it had gone on for, what area of its work was targeted and who may have been behind it; it decided it would not take its findings to Mr Shatter or the Garda, which would normally investigate matters of this nature.

Evidence of the bugging emerged during the security check carried out in the second half of last year.

It was the second such check conducted by Gsoc. The first was carried out when Mr Justice Kevin Haugh, former Irish Times editor Conor Brady and former director of consumer affairs Carmel Foley filled the three commissioner posts at the top of the organisation, having been appointed on the agency’s inception in 2006.

It found no evidence its systems had been compromised.

Since then, Mr Justice Haugh has died and his position as chairman of Gsoc has been filled by Simon O’Brien, a former officer in the London Met police force. Mr Brady’s post has been filled by former RTE journalist and Gsoc communications director Kieran FitzGerald. Ms Foley remains as a commissioner.

The Irish Times understands the three-person commission had always intended to conduct the same security sweep as its predecessors and in the second half of last year decided to act on that intention.

It is unclear what led to that action, though sources have suggested some senior staff in Gsoc viewed with suspicion the level of detail that was emerging publicly about some of its ongoing cases.

While the most contentious case currently being examined by Gsoc is the termination of penalty points by gardai, the hacking appears to predate that controversy, or at least Gsoc’s involvement in it.