Gardai involved in the Abbeylara shooting are expected to begin a High Court challenge to the Oireachtas committee investigating the incident.
In a head-on challenge to the authority of the committee, representatives of the nine gardai will seek a judicial review this week of its procedures and its authority to issue summonses.
The action is likely to lead to further delays in the work of the committee, which is currently in adjournment while the secretary to the Government considers an application by the gardai to be exempted from giving evidence.
It is understood the committee has taken advice on its legal position in the event of a court challenge. As a result, new legislation may be prepared to remove any loopholes which could prevent Oireachtas committees from carrying out their investigations.
The garda representative organisations yesterday issued a statement expressing their "grave disquiet and serious misgivings" about the way the Oireachtas was conducting its business.
The committee was not the appropriate forum to deal with the issue and a judicial review of proceedings was warranted, according to the Garda Representative Association and the Association of Garda Sergeants and Inspectors.
"The Dail committee don't have the wherewithal to do what they want to do. They don't have any authority at all," said Mr George Maybury, general secretary of the AGSI.
The committee is investigating the death of Mr John Carthy (27) in Abbeylara, Co Longford, in April last year. He was shot four times by members of the Emergency Response Unit after a 25-hour siege at his home.
At last month's hearings Mr John Rogers SC, for the nine gardai, asked for a copy of the committee's terms of reference. Yesterday Mr P.J. Stone, general secretary of the GRA, said the committee had failed to provide the information required.
"The committee is either acting within its rights or it is not. We plan to seek a judicial review of proceedings on the issue this week," he said.
Confusion surrounds the issue of whether the gardai would be prepared to give evidence to the committee if they were allowed to preserve their anonymity. ERU members fear their work could be compromised if they appeared on television.
It was reported last week that the men were prepared to give evidence provided they were not photographed. However, the representative bodies, having consulted with the gardai, now say this is not the case. Mr Maybury said they were prepared to give evidence in the proper setting of a judicial inquiry, but "not in the political forum as it exists at the moment".
The gardai had been forced to seek exemption from giving evidence because the committee had given no indication that they would be allowed to preserve their anonymity, he said.