The Public Accounts Committee has been told it does not have the legal right to investigate allegations of tax evasion.
The committee has been meeting behind closed doors to take legal advice on the dossier it received last week.
TDs have been told that the documents they received are not protected by whistleblower laws - and that they cannot interview the whistleblower himself.
It is understood that the Dáil would need to pass a formal resolution in order to give the PAC the power to investigate.
In the meantime, TDs have asked the public spending watchdog to update them on the collection of taxes due from the holders of accounts at Ansbacher bank.