The former DUP minister Jonathan Bell has denied swinging a punch at his former special adviser and trying to break his finger.
Mr Bell will give evidence to the RHI public inquiry on Thursday.
In his witness statement, published this afternoon, he says the incident never happened.
The claim was made by Timothy Cairns, Mr Bell's special adviser (Spad), who has accused him of bullying.
The witness statements further reveal the toxic relationship between the pair.
They clashed over the extent to which Mr Bell could make decisions affecting his department and the extent to which that independence was subject to control by the party centre.
Mr Bell said his perspective was that Mr Cairns saw himself as working for the other Spads, not him as the minister, and that Mr Cairns was intimidated by his colleagues.
During a row in London in 2015 one particularly heated exchange between the pair ended, Mr Bell claimed, with Mr Cairns telling him:
"Now you're going to listen to me big balls."
The then permanent secretary at the Enterprise Department was on the trip.
Andrew McCormick said he'd never seen a Spad rebuke a minister like that before.
Dr McCormick told the inquiry that the language used was "terse, pointed, it was right at the borderline of normal conversation if not a bit over it."
Mr Bell has claimed that DUP Spads sought to frustrate the introduction of cost controls in the summer of 2015 as the flawed green energy scheme spiralled out of control.
He claims one way that was done was by refusing to allow it to be included on the agenda for any meeting.
But Dr McCormick, the top civil servant in the Enterprise Department which ran RHI, said he'd no evidence to support that contention.
It has also emerged that as well as secretly taping conversations with Dr McCormick, Mr Bell also recorded a call to his then party colleague Carla Lockhart.
He also says she gave him documents relating to the Public Accounts Committee hearings into RHI in January 2017.
Mr Bell says he agreed to delay the introduction of cost controls by a month until November 2015 after being told by Dr McCormick that he had to follow the request which had come from SPADs in the First Minister's office then held by Peter Robinson.
And he claims that in January 2016 there was a row between the now head of the civil service David Sterling and DUP Spad Andrew Crawford over the scandal.
Mr Bell claims Mr Sterling suggested the massive overspend could cost him his chance to take the top job.
Mr Bell's witness statement also shows that he was taking advice from former DUP leader Peter Robinson as the closure of the scheme was considered.
They met in the cafeteria at Stormont and discussed the best way forward.
Mr Bell says the DUP later found out about the contact and appeared angered by it.
He said at a later meeting involving the then First Minister Arlene Foster and her senior adviser Timothy Johnston, Mr Johnston accused him of "crying on the shoulder of Peter Robinson".