Ansbacher whistleblower Gerry Ryan has made fresh allegations about the tax affairs of a number of former senior politicians, the Irish Independent understands.
The allegations have been made in correspondence with the Public Accounts Committee (PAC).
But members of the PAC have been precluded from accessing the correspondence following legal advice.
PAC members were told that they would be allowed to view the documentation under the supervision of the parliamentary legal adviser today.
"The legal advice I have received is that, because of a number of risks associated with receipt of such a document containing names and as the investigation of the tax affairs of any individual is not within the remit of the committee," said PAC clerk Ted McEnery.
He added that "given the risks to the committee, it should not be made available to members prior to consideration of the legal issues associated with the correspondence".
Privately, some PAC members are unhappy that they have been precluded from seeing correspondence sent to them as committee members.
Mr Ryan's dossier, sent to the PAC, alleges that a number of individuals in Fianna Fáil and Fine Gael committed tax evasion and that this was subsequently covered up.
Mr Ryan was appointed by Mary Harney in 1998 to investigate the use of a series of offshore bank accounts.
Mr Ryan claims that former politicians were named in a "Cayman ledger" in Guinness & Mahon Bank.
All politicians named categorically denied having Ansbacher accounts.