Publicising Fianna Fáil TD Michael Collins' status as a tax defaulter would have interfered with due process, the Taoiseach Mr Ahern claimed this evening in the face of Opposition onslaught over his handling of the affair.
The Taoiseach had been guilty of "appalling leadership" and "disgusting government" Fine Gael leader Mr Enda Kenny told the Dáil today.
But the Taoiseach insisted he had acted correctly by not letting the public know that Mr Collins was about to be named on a list of tax defaulters.
He told the Dáil it was not his place to put the information in the public domain.
"Deputy Collins approached me in the second half of June. He informed me personally that he had a tax issue with the Revenue Commissioners and that his name would be published shortly in the Revenue report and that when it was published he would make a public statement," the Taoiseach said.
"It was not for me to investigate the facts.
"I'm not in the business nor am I going to get into the business of due process, on breaking due process and breaking natural justice.
"There was no secret. It was an issue coming into the public domain," Mr Ahern said.
He said he had given powers to the Revenue Commissioners to catch tax cheats and that Mr Collins was a matter for them to address.
Mr Kenny, however, said the Taoiseach had fallen below the standards of propriety Mr Ahern had set down in 1998 in the wake of Haughey and Burke scandals.
Mr Kenny said: "This is appalling leadership and it is disgusting government and it does you no justice at all as leader of your party to be in here and to have to admit that you did nothing."
The Limerick TD resigned the Fianna Fáil party whip after the revelation that he once held a bogus non-resident account, but he intends to retain his Dáil seat.
Later, the Labour Party leader Mr Pat Rabbitte said"equivocation on tax evasion is alive and well" within Fianna Fáil.
He said Mr Collins should present himself to the Dáil - "rather than going to ground in West Limerick" - to explain the circumstances surrounding the affair.
"There are many questions for Deputy Collins which require immediate answers," Mr Rabbitte said.