The Taoiseach has confirmed to the Dáil that Mr Justice Feargus Flood wants to retire from the tribunal that he has chaired for the past six years.
The judge, who is aged 75, has wanted to step down for some time but has written to the Government confirming his wishes, the Taoiseach confirmed.
However, Mr Ahern said the Government would prefer if Mr Flood considered the issue of costs before he stepped down.
The Taoiseach said that even though legislation was needed, this was not a matter the Dáil should rush.
Mr Ahern said his advice was that having another member of the Flood tribunal deal with this issue did create difficulties and that there were concerns about future legal challenges.
A number of individuals, including the former Fianna Fáil minister Mr Ray Burke, may yet be forced to pay significant costs after Mr Flood cited them for failure to co-operate fully with his investigations.
Mr Flood has asked Mr Burke and others to explain why they should not pay their own costs and those of the tribunal.
The tribunal is continuing to investigate planning and payments to certain politicians and officials in the 1980s.
Mr Ahern told the Dáil this afternoon the tribunal had already cost the State €26 million and that the work already in train could take up to 15 years to complete.
Mr Flood has requested that Judge Alan Mahon, who was appointed to the tribunal last year along with another judge and a reserve judge, be asked to take his place, the Taoiseach said.