There is no "magic formula" for determining which mode of public inquiry is most appropriate to particular situations, the Attorney General advised the DIRT inquiry sub-committee yesterday.
Mr Michael McDowell SC told the sub-committee that their preference should not just be based on costs.
"The choice may well have a legal and proportionality dimension which cannot be ignored," he said.
The AG said scarcely a week went by without at least one new demand for a public inquiry being made by a public representative.
"Decisions must be made as to whether any inquiry is requisite or appropriate in such cases and if so what form it should take," he said.
Mr McDowell said different forms of inquiry were more appropriate in different situations. He cited the example of the Kerry babies inquiry.
"I don't think members of the Oireachtas would touch that issue with a bargepole and I don't think it would be appropriate for them to do it because obviously there were personal private matters concerning individual citizens and also the performance of the Garda in relation to them," he said.
He said he doubted the Garda would have been happy for a group of elected politicians to inquire into their handling of the case.
The Attorney General added that consideration also had to be given to whether a public inquiry was necessary. He cited the inquiries into sexual abuse and the inquiry into the Kilkenny incest case, which were conducted without compulsory powers.
"If you can, so to speak, click your fingers and assure co-operation with an inquiry by the likely witnesses before it, powers of compulsation may not be necessary at all. It's almost impossible to think up some paragraph or even a booklet which would tell you this is the way to go on one issue and that is the way to go on another," he said. He felt an ad-hoc approach was best.
He added that the type of inquiry chosen also depended on the life of the Dail.
"We are coming towards the end of the life of this Dail by any standards and an 18-month inquiry would simply not be a credible thing for any committee, even if members of the Oireachtas wanted to embark on it, at this point.
"I don't really think it is possible to form a judgment in advance of a situation as to what the appropriate method of inquiry is. For instance it's abundantly clear that the two tribunals at Dublin Castle are dealing with matters, which if it was the subject of a direct political inquiry by elected politicians, would not carry the same public confidence as to its outcome, I think," Mr McDowell said.
"Many people sitting on a bar stool would say surely the DIRT inquiry shows us that there is a different and better way. Yes, it has shown up very important things but it doesn't mean it can simply be transferred holus-bolus and applied to areas which are much more contentious," he continued.
Mr McDowell said he fully subscribed to a comprehensive review of all the tribunals to date, leading to legislative change.
He emphasised he was expressing his own opinions and not those of the Government.