The Mahon tribunal will have power to refuse to investigate planning corruption allegations under changes to be made by the Government.
In June the three-strong tribunal, led by Judge Alan Mahon, warned that it could take up to 11 years to finish its work unless major changes were made.
As soon as the Quarryvale module is completed, the tribunal will split into three divisions to speed up the work. These divisions will be headed by Judge Mahon and his two colleagues, Judge Gerald Keyes and Judge Mary Faherty.
The full details of the changes, which have been worked out between the Minister for the Environment, Mr Dick Roche, and Judge Mahon, will be announced formally later this week, the Government said.
The tribunal will now attempt to finish its work by March 31st, 2007.
However, if it does not meet this target, the work will continue and barristers' fees will be cut from €2,500 a day to €900 a day.
In addition to having the power to refuse to investigate allegations already made, the tribunal will not accept any new allegations 30 days after the Oireachtas accepts its new terms of reference.
Under its current rules, which were laid down by the Houses of the Oireachtas in October 1997, the tribunal is obliged to inquire into every matter brought before it.
The Dublin Castle inquiry is to be given seven extra staff by the Minister for the Environment and a €2 million increase in its budget to help speed up inquiries.
In a fourth interim report last June, Judge Mahon, who replaced Mr Justice Feargus Flood, warned that the tribunal's "onerous" workload stretched it "beyond breaking point".
He said the inquiry wanted the power to be able to drop particular investigations which it believes would "hamper or delay other, more pressing and advanced lines of inquiry".
In addition, it should be able to terminate inquiries where it believed "the conduct of its inquiries is of limited or no further value in discharging its mandate", he then wrote.
Set up in 1997, the tribunal has so far cost €33.78 million, although the final bill will be much larger because many legal bills have yet to be determined.
In recent months a significant number of people, including the Bailey brothers, have been left with multimillion euro bills after Judge Mahon refused them costs.
Although final agreement from the Opposition has not been reached to the changed terms of reference, all sides accept that some amendments must be made.
Labour TD Mr Eamon Gilmore said: "I accept that things need to be tidied up. It is going to be a never-never land unless something is done."
