DUP special adviser Timothy Cairns told then Stormont minister Jonathan Bell, "Now you're going to listen to me, big balls" in the presence of top civil servants, documents released to the Renewable Heat Incentive (RHI) inquiry have stated.
The row happened ahead of a planned meeting in London with then Secretary of State for Energy and Climate Change, Amber Rudd.
The incident, revealed in witness statements made by former DUP minister Mr Bell and published online last night, is said to have occurred in June 2015 during a ministerial visit about wind energy.
It follows previous claims of a dysfunctional relationship between the then Strangford MLA and his special adviser or 'spad', including bullying allegations made by Mr Cairns that Mr Bell "tried to break his finger and swung a punch at him".
But in documents released yesterday, Mr Bell said that "no such incident took place" and he had "no knowledge of any complaint being made".
Mr Bell was suspended from the DUP in December 2016 after outspoken comments regarding Arlene Foster's handling of the RHI scheme.
As part of his evidence to the inquiry, Mr Bell submitted recordings of a meeting and a telephone call with Dr Andrew McCormick, the most senior civil servant in his Department of Enterprise, Trade and Investment (Deti), as well as a voicemail which he had left on Dr McCormick's phone, from December 2016.
He also provided a voicemail which he had left on his former party colleague Carla Lockhart's phone, and a recording of a conversation with her.
Recalling the ministerial visit to England in his witness statement, Mr Bell said that Mr Cairns "frequently spoke over" him and "stated the Department would take a different perspective on the one that I was considering during discussions over dinner with officials".
Mr Bell described this as "inappropriate" and said it "led to tension".
Mr Bell said that he asked to speak to Mr Cairns on his own, with a view to telling him that "he could have his perspective; however it was not a spad role to overrule and contradict the Minister in front of officials and certainly not in the incoming meeting with the Secretary of State (Mrs Rudd)".
Mr Bell said: "Timothy Cairns initially refused to speak with me and a second request was made via the Private Secretary. Timothy then came into the breakfast table, he appeared agitated and when I attempted to address the issue he stated to me with his finger raised: 'Now you're going to listen to me big balls'."
Mr Bell said he was "shocked and taken aback at this outburst" and "dismissed" Mr Cairns, requesting that he "did not attend the Secretary of State meeting".
He claimed that Mr Cairns "stated he was ignoring my request and decision, and would attend the meeting regardless of my decision".
"This continued for about six statements from me including that he would ignore me as Minister and he would attend the meeting regardless of my view as Minister and that I would see what he would do with my instruction by attending the meeting and ignoring me," Mr Bell continued.
"This was embarrassingly played out in front of the Permanent Secretary and civil servants and it was only when I directed Permanent Secretary Andrew McCormick that I wanted him to ensure the Ministerial instruction was followed that Timothy Cairns while in the taxi en route to the Secretary of State's offices stated he would not now attend."
Mr Bell said that in a subsequent phone call with senior DUP spad Timothy Johnston that afternoon, Mr Johnston "stated Timothy Cairns had been told to come home and we would address the issues; however he wanted to remind me that the spads were appointed by the party officers".
Mr Bell said that Mr Cairns later "apologised for his behaviour and agreed not to interrupt or talk over the Minister" and that the "working relationship improved".
However, he said that Mr Cairns "saw himself as more accountable to the DUP spads than to the Minister, as he stated, 'Ministers come and go but spads remain'".
Mr Bell claimed that he discussed Mr Cairns' behaviour in London with Timothy Johnston and then First Minister Peter Robinson, and that Mr Robinson "stated he would not tolerate this behaviour for a moment from his spads".
Mr Bell said that he "signed to appoint" Mr Cairns as his spad and that Mr Cairns "remained the spad for the Deti Department" throughout his time as Minister.
However, he said that "for a two week period and following a dispute in London in advance of a meeting with Amber Rudd", the special adviser remained in post but "was not active in his role as spad".
During a meeting between Mr Cairns, Mr Bell and Mr Johnston, which Mr Bell said "was arranged for the purpose of Mr Cairns explaining his behaviour to me", Mr Bell said that "no allegations of bullying were discussed".
He said that "Mr Cairns returned to work and my working relationship with him was satisfactory as far as I was concerned".
Mr Bell said his working relationship with Mr Cairns had been "generally good". However, he added that he felt Mr Cairns was "intimidated" by other DUP spads.
Mr Bell also makes claims that Mr Cairns had sought to "indirectly control" him.
He said: "It is also my belief that my spad acted in a manner whereby information relating to RHI (whether generated by Deti or otherwise) was filtered and filleted so that, as Minister, I was not provided complete information.
"I believe this was a form of indirect control of my actions and decisions as Minister."
Mr Bell claimed that shortly after becoming Deti Minister in 2015, his permanent secretary had tried to raise the issue of RHI, but that Mr Cairns "stated he did not wish the RHI scheme to be on the agenda".
Following his appointment as Minister, Mr Bell said that the RHI scheme "was not included in my urgent business to address when taking over the Department but an overview was given in the general overview of the Department".
He said he was "eventually given a submission relating to RHI towards the end of August" 2015.
Mr Bell said: "It is my view that in my period as Deti Minister, pressure was exerted on me to delay the introduction of the cost control reduction by my spad Timothy Cairns, not acting on his own behalf, but under the influence of OFMDFM spad Timothy Johnston and DFM spad Andrew Crawford.
"This was exerted verbally in the form of not allowing the RHI to be discussed at the Ministerial Issues meeting.
"On one occasion, spad Cairns referred verbally to OFMDFM spad Timothy Johnston and his brother-in-law DUP Director of Communications John Robinson as having interests in the chicken industry and that was why it was so difficult to get RHI on the agenda.
"This occurred from June 2015 and was ongoing through the period of the delaying of the introduction of the cost controls."
Mr Bell said he also believed that "pressure was brought to bear on me by Permanent Secretary Dr Andrew McCormick verbally" in following the lead given by OFMDFM and the Department of Finance "both to delay the introduction of the cost controls and to extend the closure of the scheme by two weeks".
Regarding the budget for RHI, Mr Bell said he was informed by Dr McCormick that "a change had been made in previous budget under the then Minister Arlene Foster that had not been picked up in Deti that transferred significant cost to the Department from the Treasury".
Mr Bell said he was "not aware and was never made aware of any briefing or concern on a spike on demand" for the scheme.
He added that it was his understanding that Mr Cairns "interacted" with Dr McCormick and Deti's senior management team "verbally and through email correspondence".
He said: "The manner of these communications was of some concern to me. I do not believe that there was full disclosure of these communications to me - particularly in relation to RHI."
Mr Bell claimed that Mr Cairns "was in a position to (and did) exercise considerable control in respect of the agenda of the weekly Ministerial Issues meeting".
Regarding the relationship between himself and his spad, Mr Bell highlighted his understanding that the spad would be "provided with instructions from DUP party officers, other Ministerial spads, and myself as Minister".
He added: "In my experience, the fact that an instruction was given by me did not mean that it would be followed, particularly in circumstances whereby my instruction conflicted with those provided by others."
He said that there was an "accepted hierarchy" among spads, with Timothy Johnston, then the First Minister's spad, at the top, followed by Richard Bullick, also a spad to OFM, and then all other spads.
Mr Bell said that when he took up his post as Deti Minister in May 2015 he "inherited the RHI schemes that were ongoing" and "had no role in the setting up or design of the RHI scheme".
He added: "I had no involvement with the RHI scheme in period November 2012-May 2015."
Mr Bell claimed he met with Arlene Foster on February 9, 2016, and she "ordered" him to "keep the scheme open, essentially saying that she was the First Minister and by her authority I would keep the scheme open".
Mr Bell said he "passionately argued that this was folly" during the meeting, which he claimed was also attended by spads Timothy Cairns, Timothy Johnston, Stephen Brimstone, Andrew Crawford and Richard Bullick.
He added: "I was not in agreement with the outcome, but had been ordered by the First Minister to keep it open.
"The reason I disagreed with Arlene Foster was that I had been informed by my department that the schemes should be closed as soon as possible because of the budgetary pressures."
Mr Bell said that Mrs Foster "did not identify a time frame in her order to keep the scheme open".
He added that he requested a further meeting with Mrs Foster, which took place in the First Minister's office that evening.
During this meeting, Mr Bell claimed that Mrs Foster "changed her position and stated she agreed with my logic this needed to come to an end and stated she was now prepared to close within two weeks".
Mr Bell said he "agreed to take this to the Deti Deptartment" and contacted Dr McCormick, with whom he agreed to proceed.
Regarding the closure of the RHI, Mr Bell added: "My own view that the interests of industry and private businesses did not outweigh the public interest in closing the scheme sooner to minimise further public expenditure. However, I was overruled by the First Minister."