The Opposition parties have said they will raise the Taoiseach's tax affairs when the Dáil resumes in the New Year.
In a statement issued this evening, Labour leader Eamon Gilmore said that relevations in the Irish Mail on Sundaywill, if "proven correct" raise new and "extremely serious issues for Mr Ahern".
Mr Gilmore said if the reports are correct it will be "hard to avoid the conclusion that the Dáil was seriously misled by Mr Ahern regarding the status of his tax affairs, "particularly when he made a statement in the Dail chamber in September 2006."
Fine Gael's Seanad spokesman on justice, Senator Eugene Regan said that the latest disclosures in the newpaper served to further undermine the Taoiseach's credibility and demanded a clear public statement from Mr Ahern.
"According to today's Irish Mail on Sundaythe Revenue Commissioners took issue with the Taoiseach's claims that he had consulted with the tax authorities and that he had paid capital gains and gift tax.
"This latest development underlines the main point of the Fine Gael no-confidence motion that the Taoiseach has lost credibility. It is also totally unacceptable that someone who was Minister for Finance at the time and responsible for administering the tax laws of this country did not ensure his own tax affairs were in order", Senator Regan said.
He added that the issue would inevitably be the focus of close scrutiny in the Dáil when it resumes.