Michael Lowry said he is confident he can win a legal challenge against the decision to award him only a third of his costs arising from the Moriarty Tribunal.
The Chairman of the Tribunal accused the Independent deputy of deliberately delaying proceedings and ordered him to cover the majority of his legal bill, which could run to €5m.
He has told Tipp FM that he will begin a comprehensive legal challenge to the decision in the Irish Courts and if necessary take it to Europe.
"The costs are, obviously, very substantial," he said. "And I will fight all the way to ensure that I receive what I'm entitled to."
"I was forced into this tribunal [which] has lasted 15 years."
He said there was legal precedent in Supreme Court rulings for costs to be awarded on appeal.