The Labour leader called on the Taoiseach to respond to Mr Tom Gilmartin's allegations shortly after they were made on the RTE Radio programme, This Week.
Speaking to The Irish Times at the ceremony in Dublin to mark the Labour-Democratic Left merger, Mr Ruairi Quinn said the issue would be raised when the Dail resumed on Wednesday.
"There is no doubt, in my view, that the Taoiseach has to respond to what has happened. To simply suggest that these are matters for the Flood tribunal and can be left with it is not sufficient.
"In my view, he has to fill the space which has been opened up by Mr Flynn on The Late Late Show and by Mr Gilmartin on RTE Radio with some statement. Failure to do so will lead people to the inevitable conclusion that there is some substance to the allegations."
The Labour leader said it was too early to say if there were implications for the Government's stability. "It depends on what the response of the Taoiseach is and the reaction of the Progressive Democrats and the Independents supporting the Government."
Interviewed on This Week, the Fine Gael leader, Mr John Bruton, said the most important part of Mr Gilmartin's claims was the allegation that he met Mr Ahern, when he was minister for labour 10 years ago, about problems with a development, and that he had asked Mr Gilmartin to make a financial contribution to Fianna Fail.
Mr Bruton said the question arose as to whether it was normal practice for those going to see Mr Ahern as minister for labour, looking for assistance, to be asked for financial contributions.
"If this is true, he has known about it for 10 years. He set up a tribunal to investigate this. Did the Taoiseach pass on his information about his meeting with Mr Gilmartin to the Flood tribunal when it was set up? If he did not, and it happened, he has clearly failed to co-operate with the tribunal, and that in itself would be a serious matter."
