The Government has been asked to bring the costs of the long running Commission of Investigation into IBRC under control.
Taoiseach Micheál Martin has told the Dáil it is unclear if the investigation will reach a conclusion by the end of the year.
The inquiry has been running since 2015 and has yet to complete its report into the first part of its investigation.
It has been examining a write-off of €119m following the sale of Siteserv, now called Actavo. It was acquired by a company controlled by Denis O'Brien from the State-controlled bank IBRC, formerly Anglo Irish Bank.
The write-off granted by IBRC was subject of controversy and prompted the establishment of the Commission of Investigation chaired by Judge Brain Cregan in 2015.
In the Dáil today, Aontú TD Peadar Tóibín said it was expected the cost of the first module would be €14m.
The last government estimated the total cost could reach €30m, however, Mr Tóibín said the final bill could reach €70m.
He said given that it was to investigate write off of €119m he said "we need to see some level of control", he added "we are calling on the Government to get to grips with these runaway costs".
In response, the Taoiseach said the minute a government begins to cut the budget of an inquiry it opens itself to charge that it is "interfering" in an independent tribunal.
He added that once the Oireachtas decides to set up an investigation, it is then "independent" and there is "no point" complaining about the costs.