Revelations from the Moriarty tribunal relating to the Fianna Fail leader's allowance will embarrass the Taoiseach who, two years ago, insisted Mr Charles Haughey "never did anything wrong" with the £750,000 fund.
Evidence from the tribunal this week suggested three withdrawals from the allowance, a total of £60,000, were for Mr Haughey's personal use.
The Taoiseach's remarks came in July 1997 after he investigated how the allowance was disbursed when Mr Haughey was leader of the opposition.
As part of the investigation, the Taoiseach spoke to a senior administrator in Mr Haughey's office between 1983 and 1987. The person who co-operated with Mr Ahern had previously worked for Mr Jack Lynch but no longer worked for the party at the time of the investigation.
Mr Ahern said he was satisfied from this discussion that all of the £15,000 a month allowance had been paid into an Allied Irish Banks account in Baggot Street, Dublin.
The allowance had been used to pay research staff and people in the Fianna Fail press office, settle bills for hotels, press conferences and stationery and some helicopter flights. Any helicopter flights bringing Mr Haughey to his island had been paid for personally by him, Mr Ahern's investigation found.
Evidence given at the Moriarty tribunal on Wednesday indicated that two withdrawals from the leader's account in 1986 for £10,000 and £25,000 corresponded with lodgments of identical sums into Mr Haughey's bill-paying account on the same day.
Separately a withdrawal of £25,000 in 1989 appeared to have been lodged in an account in Guinness & Mahon bank which the tribunal has shown benefited Mr Haughey.