Members of a Stormont committee clashed in angry exchanges after voting to call Arlene Foster before them to give evidence on the botched Renewable Heat Incentive (RHI) scheme.
The Public Accounts Committee (PAC) agreed unanimously to call Mrs Foster and two DUP colleagues - former economy minister Jonathan Bell and former finance minister Sammy Wilson - and the former SDLP chair of the assembly's economy committee Patsy McGlone.
Under assembly conventions, serving and former ministers do not usually give evidence to the PAC.
The committee's work is more focused on value for money than policy decisions, so officials rather than politicians are called to give evidence.
Such has been the level of contention around the RHI that members have departed with convention and requested the four politicians appear before them.
The decisions were taken during a 75-minute behind-closed-doors hearing of a specially convened committee hearing at Parliament Buildings.
Shortly after the outcome was revealed in public session, the SDLP's Daniel McCrossan and DUP's Trevor Clarke were involved in an acrimonious spat.
Noting that Mrs Foster was giving evidence in relation to her past role as economy minister, Mr McCrossan said it was important her involvement as first minister was also examined.
Mr Clarke responded: "It's not hard to see that politics is being played in terms of the victimisation against one individual.
"It's unfortunate that some members want to play politics with it. It's unfortunate some members have leaked papers."
After committee chair Robin Swann said there was no confirmation any papers had been leaked, Mr McCrossan responded.
"I am not politicking," he said.
"When it comes to the waste of public money to the extent of £400 million, I think it is ridiculous that any member accuse me of politicking.
"It's about getting answers and accountability.
"This is about public money – £400 million when we can't pay teachers one% [of a pay rise].
"That's the reality people are very angry about."
Mr Clarke said Mrs Foster was on the public record saying she was willing to appear before the PAC.
"She's nothing to hide," he said.
"I know and I trust that Arlene will be forthright in everything that she brings forth to the committee."
He then accused Mr McCrossan of not taking his job on the committee seriously and questioned his attendance rate.
The SDLP man replied in robust terms.
"This is about the DUP's misconduct in this whole thing, the cover up of the thing," he claimed.
"This is not about me."
Mr Swann intervened as the men trading accusations.
"Right gentlemen, that's enough – the two of you – that's enough," he said.
