Joe Higgins has said the current laws on Oireachtas inquiries are not fit for purpose, and should never be used again.
The Socialist TD was commenting after he announced he would not sign off on the final report of the Banking Inquiry, of which he is a member.
In an open letter to the Inquiry Chairman, Ciaran Lynch, he says it was inevitable that a majority of members would support the status of banks, and he could not sign their report as a result.
But he says the law governing the Inquiry makes it too difficult to even ask a straight question of many witnesses.
Mr Higgins said: "Whereas I am satisfied that the essential questions from my point of view were put, I think the legislation should allow the questions to be put in a more forthright and robust fashion."
There has been no confirmation of reports that the document contains a recommendation that the State launch legal action against the European Central Bank over its stance on burning bondholders.
The report itself will now undergo three days of legal checks before a copy is sent to witnesses and the remaining nine members will hold their breath and hope a legal challenge does not follow.