The Moriarty Tribunal has cost the State more than €61m so far, the Public Accounts Committee has heard.
The investigation into the financial affairs of former Taoiseach Charles Haughey and former Fine Gael communications minister Michael Lowry is expected to cost €4.5m this year.
The tribunal was set up in 1997 and continues to cost the state.
The country’s most senior civil servant, Secretary General of the Department of the Taoiseach Martin Fraser, told the Public Accounts Committee that Commissions of Investigation are better that tribunals in financial terms.
He said they are quicker, cheaper and “better in terms of spending” and that caution needs to be taken before the setting up of tribunals.