New allegations had been made against the former Fine Gael TD and senator, Mr Liam Cosgrave, by Mr Frank Dunlop, Mr Michael O'Higgins SC, for Mr Cosgrave, told the tribunal.
"It is a matter of fact that after 12 to 13 days of Mr Dunlop's evidence and three months into this module, my client is now faced with new allegations," Mr O'Higgins said.
This included an allegation of an additional payment.
The reaction of the tribunal to the allegation had caused them grave and serious concern.
The witness was not asked by tribunal members as to how the allegations were made for the first time.
"That man has been allowed to make new allegations against my client, and the tribunal has not raised as much as an eyebrow," Mr O'Higgins said.
Mr Dunlop was directed by the tribunal last Wednesday to make a list of names and a statement. Mr O'Higgins said they expected an apology from the tribunal for suddeny being faced with a new set of allegations when they were preparing their case.
"What did we get? We got a letter written in a tone that was coercive and bullying," Mr O'Higins said.
The letter wanted a response on the new allegations before Mr Cosgrave knew what the allegations were.
Mr O'Higgins said: "The tribunal must be based on fair procedures, and if there is a set of new allegations my client must know what they are."
Mr John Gallagher SC, for the tribunal, said the tribunal was a public inquiry, and very often of necessity material which was not known would emerge.
If the tribunal was to carry out meaningful inquiries in private, it must be able to write letters and elicit answers so that people could be forewarned.
Mr Gallagher said he rejected criticism of the letter as it was a request for information.
The chairman, Mr Justice Flood, said he rejected the suggestion that the tribunal had acted in a manner not consistent with fair procedures. At a public inquiry new matters would arise in oral evidence.
Mr Cosgrave was not ordered to make a statement, he was only invited. Mr O'Higgins's description of the tone of the letter was wholly inaccurate and misleading, the chairman said.
Mr O'Higgins said that the tribunal had made a finding of fact that he had overstepped the mark and he apologised.