Mahon tribunal chairman Judge Alan Mahon has angrily rejected what he said was an accusation by the Taoiseach's lawyers that the tribunal was on "some twisted, illegal, corrupt frolic" with an agenda against Mr Ahern.
In a series of extraordinary exchanges this morning between Judge Mahon chairman and Conor Maguire, SC for Mr Ahern, the chairman accused Mr Maguire of "disgraceful" allegations that the tribunal judges were under the influence of counsel and that they were not independent.
Judge Mahon said Mr Ahern's lawyers were making an allegation that the judges had been influenced by tribunal counsel in making a ruling on matters affecting Mr Ahern today.
"Now that is a disgraceful comment, and I absolutely reject it," Judge Mahon said. "You are making an allegation, and you have said it before that we are pursuing some sort of agenda."
He said that if the tribunal was following the agenda it was accused of, the effect of the allegation "is that you are saying we are crooks, that we are conducting a witch hunt".
The judge said Mr Maguire was making certain statements "for a purpose" and so there would be newspaper headlines tomorrow stating that Mr Ahern's counsel had "attacked the tribunal and accused us of avoiding our responsibilities".
The judge said that Mr Maguire was making "the most serious allegation because it is the one that if established to be true would completely undermine the work of the tribunal".
He said that if Mr Maguire believed this he "should have gone to the High Court long ago" to say the tribunal was "engaged in an agenda".
Mr Maguire said he was not going to use the "emotive" language used by Judge Mahon.
He said he did not make an apology for stating that tribunal counsel had an agenda and that he had said it publicly. "I know that you are doing the best you can in all the circumstances," Mr Maguire said.
But he said that "unfortunately" the circumstances were that "one side of the argument has access to you and the other doesn't".
Judge Mahon said Mr Maguire was "suggesting we are under the influence of our counsel to the extent that our decisions are in some way tainted".
"We exercise absolute independence and we are most careful that we do that." The judge said he would treat any legal submission ever made "with respect and we always give it consideration".
There were cheers of "hear hear" and applause from the public gallery on a number of occasions as Judge Mahon spoke. The tribunal rose for a short break after the exchanges.
Mr Ahern took the stand after the break and is again being questioned on his financial affairs.
Yesterday, the tribunal heard Mr Ahern made a voluntary disclosure to the Revenue Commissioners in 2006 about a £5,000 cheque he used to open a building society account in Drumcondra in January 1994, when he was minister for finance.
Mr Ahern said he could not recall with certainty who had given the cheque to him. He described it as "a political donation, for my personal use".
He said he and his legal team had "trawled" for the records of the amounts but had not been able to match the £5,000 cheque up with a donor.
He was sure he knew the name of the individual and the company from which it had come. However, although he went back to the company "three or four times", and that company was "very helpful", it was not in a position to confirm it was the source of the £5,000.
The head of the company was dead, he told the tribunal.
Mr Ahern indicated that over the years he had on a number of occasions been given personal financial gifts that he had accepted.