The briefing note supplied by the Garda Síochána Ombudsman Commission to the Minister for Justice Alan Shatter seems to contradict his comments last night that he set out to the Dáil the information furnished to him.

The three-page briefing note, which has been seen by The Irish Times, includes a number of specific details which were not referenced by Mr Shatter in his statement in the Dáil on Tuesday. The note also seems to reflect, in summary form, the account given by GSOC chairman Simon O'Brien to the Oireachtas Committee on Oversight and Petitions during four hours of hearings.

Mr Shatter last night said that the three-person GSOC commission had given different answers to particular issues. “Some of what was said during the course of that was to be a little confused or contradictory”, Mr Shatter said during an interview on RTÉ’s Prime Time last night.

However, an examination of the briefing note by The Irish Times indicates that the evidence given by Mr O'Brien and the other commissioners to the committee is largely consistent with the information contained in the briefing note it submitted to Mr Shatter before he made his Dáil statement. It includes information that was divulged to the committee but was not disclosed by the Minister when speaking in the Dáil on Tuesday evening.

However, the briefing note does not contain any reference to a context or “trigger” for the initial security sweep – Mr O’Brien revealed on Wednesday there were specific concerns and reasons that prompted the sweep.

While Mr Shatter quoted from the briefing notes in the Dáil on Tuesday, he did not include some of the details in relation to two of the three specific potential security threats that were identified that would tend to increase the gravity of the threat posed to the security of the GSOC’s offices.

One of the potential threats concerned a telephone in Mr O’Brien’s office. The test involved sending an audio signal down the line to see if somebody was listening in. The note, and Mr Shatter’s Dáil statement, both stated that immediately after the transmission of the audio signal, the conference phone rang.

However, the briefing note – and subsequent comment by Mr O'Brien and fellow commissioner Kieran Fitzgerald – went on to say that the operator from the UK security company Verrimus "judged that the likelihood of a 'wrong number' being called at that time (1am), to that exact unknown number, at the time of an alerting text, was so small as to be at virtually zero".

There is no reference to this sentence in Mr Shatter’s Dáil statement which rather emphasises another point in the briefing that no further anomalies were discovered.

On the third threat there is another omission from Mr Shatter’s Dáil statement. That related to an “unexpected 3G network” detected in the vicinity of the GSOC offices. Mr Shatter did not disclose to the Dáil any further details of this network other than it suggested that UK phones registered to that network making calls would be vulnerable to interception. The Dáil statement did not specify that it was not a network that might be operated by a mobile telephone company rather a specific operation established – according to the security company Verrimus – for clandestine purposes.

The briefing stated: “[VERRIMUS] advised that such a network can only be simulated through a device called an ISMI catcher. An ISMI catcher, in simulating a UK mobile phone network, will pick up UK phones register to that network.

“Once a phone has been connected to that ISMI catcher, it can be forced to disable call encryption making the call data vulnerable to interception and recording. The specialist firm indicated that this level of technology is only available to Government agencies.”

Mr Shatter made no reference to that detail, particularly to the sophisticated nature of the simulated network and its Government-level status in the course of his Dáil statement.

In addition the briefing from GSOC to the Minister also stated that on the foot of the first two threats identified, the GSOC’s acting director of investigations was of the opinion that if any of the threats could be proven, the surveillance may have originated from An Garda Síochána and, if so, a member of An Garda Síochána may have committed an offence.

Mr Shatter made no reference to An Garda Síochána being included within the circle of possible suspects in his statement.

He said in the Dáil: “I understand that no connection between any member of An Garda Síochána with any of these matters arose. This is not my conclusion, it is that of the GSOC.”

While the briefing did conclude that no definitive evidence of an authorised or electronic technical surveillance was found, as Mr Shatter noted, it did find that there were anomalies that “could not – and still cannot – be explained.” The briefing note, however, did also accept that reasonable and innocent explanations for any or all of the issues could be found, including the ISMI watcher (the UK network) being used for a legitimate operation on another target in Capel Street or the phone call that was received at 1am being an “innocent call”.

Speaking on RTÉ’s Prime Time last night, Mr Shatter said he “went into the Dáil and set out the information furnished to me. That is the position and remains the position.”

Both chairman of the oversight committee, Pádraig Mac Lochlainn and Fianna Fail's justice spokesman Niall Collins have challenged that version, saying that there was much additional information contained in the briefing that Mr Shatter did not divulge in the Dáil. Mr Collins said today that Mr Shatter should clarify in the Dáil what was said to him by GSOC.

Sinn Féin and Fianna Fáil have contended that, by omission, he downplayed the nature of the anomalies and potential threat when addressing the Dáil on Tuesday.

Yesterday, both parties also questioned the assertion made by Mr Shatter on RTÉ last night that at no stage during his oral briefing or his written brief did [MR O'BRIEN]state that he or GSOC believed they were under surveillance.

“What was stated was that in the context of a security sweep that was taken, vulnerabilities or potential threats or abnormalities had been identified. I acted on foot of that,” Mr Shatter told RTÉ.

Asked on Prime Time had Mr O’Brien and GSOC not told him the full story, Mr Shatter said: “I was told the story that I told the Dáil. I do think there is confusion from the four hours of hearings that took place the following day before the Oversight committee].”

In one respect, Mr Shatter’s criticism is borne out. He said last night that Mr O’Brien had told him that GSOC had commissioned the security sweep on a routine basis. “No threat was ever identified as stimulating the need for such a sweep,” he told Prime Time.

The written briefing makes no reference to a specific “trigger” for such a sweep, although Mr O’Brien told the Oireachtas Committee that there was indeed a context that prompted the Commission to decide to conduct a sweep.