A source close to Prince Andrew says the Queen's son has "dozens of email exchanges" which vindicate him in his public spat with US investigators.
Prosecutors from the Southern District of New York have repeatedly accused Andrew of refusing to sit down for an interview with their investigation into the underage sex ring run by his disgraced friend Jeffrey Epstein.
Less than two weeks ago, US Attorney Geoffrey Berman said the Duke of York was trying to "falsely portray himself to the public", and had informed prosecutors "unequivocally" that he would not give an interview.
Berman had previously accused Andrew of putting up a "wall of silence", news.com.au reported.
Andrew's legal team, meanwhile, insists he has offered to help investigators on multiple occasions.
The unnamed source, described merely as someone "close" to the Duke, has spoken to the American edition of The Spectator and reinforced the arguments of Andrew's legal team.
"Berman has actively misled the global media and the global audience," the source claims.
"The Duke's legal team has dozens of email exchanges with the Southern District, proving that there has been full co-operation."
The source says Berman "must have known we had an email trail". Note their use of the word "we". It's rather clear whose side they are on.
They also accuse the Southern District of being a "water carrier" for commercial law firms representing Epstein's victims, who are trying to secure financial settlements from the dead sex predator's estate.
The problem, in this telling at least, is not the Duke's "willingness" to co-operate so much as a "collapse of trust" caused by Berman's "grandstanding".
The catalyst for this eruption of public insults between prosecutors and Andrew's legal team came in early June, when the US Department of Justice (DOJ) filed a mutual legal assistance request to Britain's Home Office.
That move amounted to a demand that Britain hand over the Duke to be interviewed.
Last Monday, Andrew fired back through his lawyers at Blackfords LLP, Clare Montgomery and Stephen Ferguson.
They said the DOJ had been "actively investigating" Epstien for 16 years, but had never requested Andrew's co-operation until January 2 this year.
"The Duke of York has on at least three occasions this year offered his assistance as a witness to the DOJ. Unfortunately, the DOJ has reacted to the first two offers by breaching their own confidentiality rules and claiming that the Duke has offered zero co-operation," they said.
"In doing so, they are perhaps seeking publicity rather than accepting the assistance proffered."
Berman immediately hit back.
"Today, Prince Andrew yet again sought to falsely portray himself to the public as eager and willing to co-operate with an ongoing federal criminal investigation into sex trafficking and related offences committed by Jeffrey Epstein and his associates, even though the Prince has not given an interview to federal authorities, has repeatedly declined our request to schedule such an interview, and nearly four months ago informed us unequivocally – through the very same counsel who issued today's release – that he would not come in for such an interview," the US Attorney said in a statement.
"If Prince Andrew is, in fact, serious about co-operating with the ongoing federal investigation, our doors remain open, and we await word of when we should expect him."
Months earlier, back in March, Mr Berman said the Prince had "shut the door" entirely on US authorities. This too, drew the ire of Andrew's lawyers.
"These statements were inaccurate, and they should not have been made," they said.
"It is a matter of regret that the DOJ has seen fit to breach its own rules of confidentiality, not least as they are designed to encourage witness co-operation.
"Far from our client acting above the law, as has been implied by press briefings in the US, he is being treated by a lower standard than might reasonably be expected for any other citizen.
"Further, those same breaches of confidentiality by the DOJ have given the global media – and, therefore, the worldwide audience – an entirely misleading account of our discussions with them."
The current furore comes just weeks after a Netflix documentary on Epstein was released featuring Virginia Giuffre, also known as Virginia Roberts, who has alleged she was forced to have sex with the Duke of York in 2001 after being trafficked to the United Kingdom by Epstein.
The Duke categorically denies he had any form of sexual contact or relationship with Giuffre.
Andrew was forced to step down from his royal role following a disastrous Newsnight interview in November about his relationship with Epstein.
Rather than draw a line under allegations, it raised more questions than answers, particularly given Prince Andrew's bizarre claims that he didn't sweat and had a Pizza Express alibi.
Four days after the interview, the Duke said in a statement he was "willing to help any appropriate law enforcement agency with their investigations, if required".