The Government's inquiry into the recruitment of PR consultant Ms Monica Leech by the Department of the Environment is to be headed by a senior former civil servant.
He was named this evening as Mr Dermot Quigley, who is a former chairman of the Revenue Commissioners.
The Government investigation will run in parallel with a preliminary inquiry ordered last week by the State's independent ethics watchdog, the Standards in Public Office Commission.
The Taoiseach, Mr Ahern, said at the weekend it is hoped the two inquiries will be finished within a month.
Ms Leech, a political supporter of Mr Cullen from his Waterford constituency, has earned €300,000 since the Department of the Environment hired her as a part-time consultant shortly after Mr Cullen was appointed Minister for the Environment in June 2002.