Mr Frank Dunlop has called on politicians to follow his example and "fess up" before the tribunal.
He said he was not putting himself forward as a model for other witnesses, but it would serve everyone's interest and time if "some people" took a similar line to his.
Asked why people should believe his evidence now, he said: "I have nothing to gain by coming in here and telling the story other than it is."
He had been "wrong and stupid" to conceal his involvement in the bribing of councillors when he first gave evidence in April 2000. However, from the moment Mr Justice Flood had asked him to reflect on his evidence, his life had changed dramatically.
"I have no employment, I have no business, I have no clients . . . those people with whom I had a strong personal relationship, including politicians and clients, regard me as something of a pariah. But I accept that."
When he first came to the tribunal, he had lied to his own legal advisers and made deliberate omissions from his statement. There was no other word for what he had done, albeit with the involvement of others. He apologised to the chairman for his actions.
Mr Dunlop yesterday admitted he lied on numerous occasions when he first gave evidence to the tribunal over two years ago.
Mr John Gallagher SC, for the tribunal, reviewed Mr Dunlop's original evidence. In more than a dozen cases, the witness agreed that he had lied.
Mr Gallagher also pointed out that when, over two years ago, Mr Dunlop finally furnished names of councillors to whom he allegedly made payments, he failed to mention all those people he now claims to have paid off.
Those he did not mention in 2000 were: Sean Gilbride, Cyril Gallagher, Don Lydon, Jack Larkin and John O'Halloran.
Mr Dunlop explained these omissions by saying that it was only after giving evidence, when he checked council documentation and followed the "road-map" of the County Development Plan, that he recalled the additional names.
Earlier, Mr Gallagher revealed the tribunal has failed to find any evidence in the bank accounts of county councillors of payments allegedly made to them by Mr Dunlop.
He said the tribunal had carried out extensive investigation and analysis of the financial affairs of the politicians figuring in Mr Dunlop's allegations.
These had failed to show any "definitive indications" that money Mr Dunlop said he paid to the councillors was lodged to their bank accounts.
The tribunal will examine the financial records of the politicians in detail at a later stage.
Mr Dunlop has now completed his direct evidence; cross-examination begins on Tuesday.
