Assembly Member Jimmy Spratt has angrily denied calling people who object to the Maze peace centre as "nutters" and said he was seeking legal advice after the claim by Ulster Unionist leader Mike Nesbitt.
The DUP man claimed the word was taken out of context from a private conversation during a heated meeting of a Stormont committee.
The UUP leader had insisted he heard the description used in the committee that scrutinises the Office of the First and Deputy First Minister yesterday.
Later, Mr Spratt said he did use the word "nutters" – but that it was totally unconnected to the Maze.
The two politicians had taken part in an angry exchange in the committee.
First Minister Peter Robinson had been telling MLAs at the committee he was convinced there would be "nothing in the centre to offend anyone".
The DUP and Sinn Fein have backed the controversial prison site development but Mr Nesbitt fears that it could end up as shrine to IRA terrorism. Making the accusation at the Stormont meeting, committee chairman Mr Nesbitt told the DUP MLA: "I know what you said, Jimmy."
Mr Spratt angrily retorted by claiming the recorded account of the committee meeting could verify his version of events, although Hansard's official reports are not immediately available.
The South Belfast MLA told Mr Nesbitt: "You are absolutely pathetic in terms of how you try to spin things."
Speaking after the meeting, Mr Spratt said Mr Nesbitt had heard him use the word "nutters" in a private conversation he was having with a colleague.
"I certainly said nutters but that word was not used about the Maze," he said.
"It was a private conversation, no business of the committee.
"The chair is meant to be impartial."
Mr Spratt added: "He should apologise for the remark he made. I am also seeking legal advice."
Mr Nesbitt was unavailable for comment last night.