Taoiseach Bertie Ahern has "diminished" his office by his testimony to the Mahon tribunal over lodgements to his accounts in the early 1990s, Fine Gael leader Enda Kenny has said.
The language used by Mr Kenny marks a significant sharpening of tone in his handling of the controversy in advance of the Dáil's resumption tomorrow following the summer recess.
Mr Ahern will return this afternoon for further questioning before the three-judge tribunal. He has already been subjected to three previous days of questioning and there is no guarantee that today will mark the end of his evidence.
Following up on warnings given in Galway two weeks ago that he would adopt a more combative stand against the Taoiseach, the Fine Gael leader last night said: "He has the opportunity to go and clear this up. The truth is always simple."
He added: "I find it quite extraordinary that a person who has been eulogised by the media for his mastery of detail for some strange reason cannot remember extraordinary amounts of money - paid in cash - moving through his accounts."
Later, he said: "I think that sends out a certain message about the way that standards are accepted here, and the way that business is done. I feel that the office of An Taoiseach is diminished by all of this."
The Government will come under attack this week in the Dáil from the Opposition on a number of fronts, including the ending of Aer Lingus flights from Shannon to Heathrow and the state of cancer services.
Following three difficult days for Mr Ahern before the tribunal, it is clear, however, that both Fine Gael and Labour believe that his evidence has exposed weaknesses that can now be exploited.
However, Fine Gael, despite speculation, has not yet decided if it will put down a motion of no-confidence in Mr Ahern - though the odds, for now, are against it, even though a senior party official refused to rule it out yesterday.
Under the rules of the Houses of the Oireachtas, motions of no-confidence can be put down only at six-monthly intervals, and there is no prospect that one now would have any chance of success.
Meanwhile, Minister for Finance Brian Cowen has said that he hopes that the Mahon tribunal "is coming near the end of its deliberations".
He continued: "We certainly need to learn lessons for the future, as to what mechanisms can be best used to inquire into matters of urgent public importance.
"The need for clear and specific remits would help the Oireachtas in future to establish an indicative time-frame within which taxpayers and citizens, generally, could reasonably expect the examination to reach its conclusions," he told the Sunday Independent.
Speaking in Paris on Saturday, Mr Ahern said none of the issues being investigated by the Mahon tribunal would have occurred if he had not separated from his wife, Miriam.
"I think you would see that people who are separated have to do different things at different times to survive and to move on and I did the same," he told journalists.
Insisting that Mr Ahern's private life is not his business, the Fine Gael leader, speaking on TV3's The Political Party, said: "When you have a witness in before a tribunal continuously changing his story it does create a credibility problem."
Rejecting Mr Ahern's complaints about the time he has had to spend in the witness box, Mr Kenny said much of the blame for that lay with the Taoiseach himself.
"I accepted the Taoiseach's word that he wanted to go in before the tribunal, that he wanted to give clear answers and that he wanted this finalised once and for all.
"To date, in the evidence that he has given, I have not heard any credible account in that regard. I have heard rambling, incoherent answers.
"The fact that no Minister in his Cabinet is prepared to say that what was done was wrong I find it quite incredible."
