GARDA Ombudsman Commissioner Kieran Fitzgerald has refused to rule out bugging at the watchdog's offices.
He said he agreed with Justice Minister Alan Shatter that there was no evidence found of bugging, but that he could still not be certain whether or not it had actually happened.
"It would be very, very good if we were able to say definitely yes or definitely no. Unfortunately the reality of modern surveillance is that it is very often an inconclusive result," he told RTE's 'Prime Time' last night.
"What we are faced with at the conclusion of this is that we could more or less dismiss some of these threats on the balance of probability. On others we just do not know."
Mr Fitzgerald added: "I don't think there's any reason for any of us to consider our positions.
"I would absolutely refute the suggestion that this was foolish. We got an expert group to report a credible threat to our security. We did everything possible and thoroughly to try to identify and eradicate that possibility."
He said they will not publish the report because "it reveals far too much about the security of our organisation".
Earlier, the Government confirmed it still has confidence in GSOC, with Mr Shatter saying he has "no beef" with the organisation.