The Public Accounts Committee has been told it cannot hold a private meeting with a whistleblower behind allegations of tax evasion.
Gerry Ryan had written to the committee asking for a private hearing to discuss the allegations made last year.
But the committee this morning heard legal advice that the matter is outside its remit, and that if Mr Ryan gave evidence, it would not be privileged.
TDs have therefore decided not to invite Mr Ryan for questions, and to close any investigation.
The issue is still being considered by Gardaí who have passed previous files to the DPP.