Mr Ray Burke told the Taoiseach, Mr Ahern, he had control over a political fund, which contained £118,000, on the night of the by-election for his former seat in Dublin North in 1998.
He said he told Mr Ahern about the fund, but "not the extent of it", during a "wide-ranging" conversation in a Swords pub.
"It was after the polls closed on the night of the election. It was the first occasion that I had personally met the Taoiseach from the time I resigned in October 1997," he said. About a month later, Mr Burke said, he told Mr Des Richardson, who was in charge of fund-raising for the party, about the fund.
In response to a question from the tribunal chairman, Mr Justice Flood, Mr Burke said that before telling the Taoiseach and Mr Richardson, he had told no one in the party about the fund.
He said TDs never discussed their own personal fund-raising, and if Fianna Fail headquarters had discovered the fund it would have tried "to secure some of it". He said he would not have expected Mr Ahern or any other TD to ask about his personal fundraising.
He said such fund-raising was an unfortunate fact of political life and happened because TDs salaries were so inadequate for the level of demand placed on them. "They couldn't possibly meet it out of just Dail funds. They have to do fund-raising," he added.
Counsel for the tribunal, Mr John Gallagher SC, asked: "Did you tell the Fianna Fail party you hold £118,000 in trust for that party and for their benefit?"
Mr Burke said: "I didn't say it was in trust for that party. I have been very careful in the wording that I used, that the funding, the political fund is still there. It exists, and I have to take legal and accountancy and tax advice in relation to it".
He added that because he had retired from public life he would not benefit from it.
He said Mr Justice Flood should draw attention in his report to the whole area of political fund-raising which had left him open to some of the allegations which had been made. "It is me today and someone else in the future," he said.