The Government has set aside €30 million this year to pay for costs arising from the Mahon tribunal report.
The Public Accounts Committee heard today, however, that this amount may only be a fraction of the final bill for the tribunal.
The secretary general of the Department of the Environment, Geraldine Tallon, said that, based on advice from the tribunal chairman Judge Alan Mahon, the final bill could be from between €204 million and €250 million.
She said €97 million has so far been paid out in relation to costs of the tribunal.
Fine Gael deputy John Deasy, who suggested the final tribunal report may emerge next week, questioned where the balance of the €150 million would come from.
Ms Tallon said there was no provision made in the Department of Environment in relation to third-party costs awarded in recent years by the tribunal. She said third-party costs that had been paid out to date related to the period up to 2002.
Ms Tallon said when third party costs had been submitted to the department, they had been "interrogated" and sent to a legal cost accountant. The department has secured reductions of 30 per cent on average on the bills submitted, she told the hearing.
The Department of Public Expenditure and Reform said provisions had been made in the 2012 accounts for payment of €30 million to cover Mahon tribunal costs. However, it said this is only in relation to 2012.
Committee chairman Fianna Fáil’s John McGuinness said a key issue will be the decision of the tribunal on third party entitlement to costs.
Mr McGuinness said: “No provision has been made in the accounts of the department nor is there a note signifying a contingent liability in respect of these costs”
"The committee will want to know the basis of these estimates, the likely time frame in which the taxpayer will have to meet these costs and the extent to which many more lawyers will become millionaires as a result of the work of this Tribunal that was appointed 15 years ago,” he said.
The tribunal is due to publish its final report in the coming weeks.
Its final report will deal extensively with allegations made about a number of Fianna Fáil figures, including former government press secretary Frank Dunlop, former EU commissioner Pádraig Flynn and deceased TD Liam Lawlor. It will also address the financial affairs of former taoiseach Bertie Ahern.
The Tribunal of Inquiry into Certain Planning Matters and Payments - its official title - was established by minister for the environment and local government, Noel Dempsey in November 1997, and has held 917 days of public hearings with 400 witnesses.
Its initial remit was to inquire into the planning history and ownership of 726 acres of land in north Dublin and to investigate any payments to politicians or officials in connection with its rezoning.
However, its terms of reference were soon expanded to allow for the investigation of all suspect payments to politicians and local authority officials in connection with a spate of re-zonings in Dublin.