The former Fine Gael minister Michael Lowry said the tribunal has taken over his life and become "a cancer".
Mr Lowry was giving evidence for the second day to the tribunal's ongoing public inquiry into whether he had any involvement with a £3.8 million property transaction in Doncaster in 1998.
Mr Lowry told the tribunal he had no involvement in the transaction, which businessman Denis O'Brien has told the tribunal was his exclusively.
He said that since the passing of the late Charles Haughey he, Mr Lowry, had "the dubious distinction of having a tribunal all to myself. I'm sitting here as the chief one being inquired into. I have the role all to myself."
The tribunal was set up in 1997 to inquire into payments to Mr Haughey and Mr Lowry. Mr Lowry said he was depending on the chairman, Mr Justice Michael Moriarty, to be fair and balanced.
"I want to get out of here," he said. "I've had enough of it. I'm weary, I'm tired of it. This tribunal has taken over my life," he said. "This tribunal has been a cancer to me." The tribunal has had "a massive impact" on him emotionally and intellectually.
Jerry Healy SC, for the tribunal, asked Mr Lowry if he wished to comment on the fact that two documents, from 1998 and 1999, mentioned him in relation to Doncaster. Mr Lowry said he was "not concerned any more about what's in documents. I am concerned about the facts and the fact is that I had no involvement in Doncaster."
Mr Healy asked about the letter written by the English solicitor Christopher Vaughan to Mr Lowry in 1998 which was based on the presumption that Mr Lowry was involved in the Doncaster transaction. Mr Healy said Mr Vaughan had subsequently stated that he may have written the letter because of Mr Lowry, a politician, making claims that he was involved in the Doncaster project, when this was not the case.
Mr Lowry said he "may be in a bravado mood from tomorrow when I start the election campaign", but he had not been in such a mood when he met Mr Vaughan in 1998.
He had no involvement in Doncaster. "If something was said that led him to that view, then it was erroneous," Mr Lowry said. "Whatever impression was formed, it was a mistaken impression." Mr Lowry said no one had ever shown him a copy of the letter or a copy of a 1999 fax that contained a reference to an "ML" in relation to the Doncaster deal, until those documents had been discovered by the tribunal.
He said that his accountant, Denis O'Connor, visited Mr Vaughan in 2002 to discuss the letter but he, Mr Lowry, was not shown a copy of it. He said that Mr O'Connor reported back that Mr Vaughan had said the letter was "a load of nonsense".
The tribunal has heard that Mr O'Connor became involved in settling disputes over money with Northern Ireland businessman Kevin Phelan in relation to a range of property deals in the UK with which Mr Phelan was involved. Mr Lowry was connected with some of these deals and Mr O'Brien with the one in Doncaster.
Mr Lowry said he had not wanted Mr O'Connor involved in this way but once he was involved he asked him to look out for some aspects of his, Mr Lowry's, interests.
Mr Lowry concluded his evidence and the chairman said he was "free to take up his other interests". The tribunal adjourned to a date to be announced.
