The Taoiseach has told the Dáil that he did not mislead the Dáil in relation to his personal finances.
Opposition leaders have been challenging Bertie Ahern about his High Court challenge to the Mahon Tribunal.
Mr Ahern said he had clear legal advice that it would not be correct for him to answer questions on statements he made to the Dáil and that the substance of what he said had been repeated outside the house.
However, Labour leader Eamon Gilmore said Mr Ahern was either trying to hide something or to buy time.
Mr Gilmore said the Taoiseach's court action was nothing to do with parliamentary privilege but about protecting himself. He said the Taoiseach's last minute rush to the court was to play for time and prevent the tribunal from asking questions.
In response, the Taoiseach said it was about respecting the Constitution and the law.
He reiterated that he had no difficulty answering questions in the tribunal but he would not answer questions circulated or said in the Dáil. He said that, following legal advice, he must stand by Article 15.13 of the Constitution.
No advance notice
The Green Party and the Progressive Democrats have confirmed that they had no advance notice of the Taoiseach's intention of launching a legal challenge to the Mahon Tribunal.
John Gormley and Mary Harney were informed of Mr Ahern's intentions in a telephone call between noon and 1pm yesterday.
A spokesman for Mr Ahern said he understood that Fianna Fáil Ministers were informed of the development at around the same time.
Both the Greens and the PDs say that Mr Ahern's action is being taken in a private capacity, not as Taoiseach, and that they were therefore content to allow the courts to decide the matter.
However, Mr Ahern told the Dáil that he had a special responsibility as Taoiseach to ensure that the rights of TDs were upheld.
It is understood that the legal challenge was not discussed at today's meeting of the Cabinet.
Opposition fear tribunal delay
Earlier on RTÉ Radio, Fine Gael leader Enda Kenny claimed there was a serious gap between the information provided by the Taoiseach to the Mahon Tribunal and statements he made in the Dáil in 2006.
Mr Kenny said he did not accept that Bertie Ahern had no alternative but to lodge the High Court challenge. Mr Kenny then suggested the Taoiseach could have rejected the advice of his legal team.
He added that Mr Ahern's move could well have the consequence of delaying the tribunal and increasing its costs.
Last month, Government TDs backed a motion in the Dáil affirming confidence in the Mahon Tribunal, and looking forward to receving its report 'expeditiously'.
But Opposition parties claim the tribunal's work will be delayed by the Taoiseach's High Court challenge to three aspects of its investigation into his personal finances.
