Also on Monday, the US Attorney's Office of the Southern District of NY released a statement claiming that "Prince Andrew yet again sought to falsely portray himself to the public as eager and willing to cooperate with an ongoing federal criminal investigation into sex trafficking and related offenses committed by Jeffrey Epstein and his associates".
USA investigators want to interview Andrew, Queen Elizabeth's second son, about his friendship with Epstein as part of their inquiry into possible co-conspirators.
A statement from his lawyers Blackfords LLP said: "The Duke of York has on at least three occasions this year offered his assistance as a witness to the Department of Justice".
The response comes after the US Department of Justice lodged a Mutual Legal Assistance (MLA) to the British government to speak with the 60-year-old, who was friends with Epstein, as part of their inquiry into the many claims made about him by those who say he trafficked them for sex.
A spokesman for the US Attorney's office for the Southern District of New York, Nick Biase, said: "I can not publicly comment on communications with foreign governments on investigative matters, including confirming or denying the very existence of such communications".
His lawyers, however, state that he has already cooperated with them in their investigation.
Virginia Giuffre, a key Epstein accuser, has said she was forced by Epstein to have sex with Prince Andrew.
One woman, Virginia Roberts Giuffre, claims Andrew had sex with her when she was still a minor, a claim he emphatically denies.
A number of businesses and institutions have since distanced themselves from him and he has stepped back from royal duties.
Following his "car crash" interview with Emily Maitlis on the BBC, Prince Andrew's behaviour was highly criticised.
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The accounts were linked to the Proud Boys and the American Guard, which are already banned on Facebook. When Trump made the same statements on Twitter , it put warning labels and fact-checks on his tweets.
They also accused the DOJ of "breaching their own confidentiality rules" by publicly claiming that the duke had been uncooperative.
In a new phase of a scandal that has rolled for months, federal prosecutors in NY have now officially asked for permission to speak with Prince Andrew, who has always been linked with dead financier Jeffrey Epstein.
In January, Geoffrey S. Berman, the United States attorney in Manhattan, called out the prince for his alleged lack of cooperation.
Barr's comments came only hours after Andrew's attorneys said they've been assured by the DOJ that he was not a target in the Epstein investigation.
She said Epstein flew her around the world on private planes to have sex with powerful men, and that she had sexual encounters with Andrew in London, New York and in the U.S. Virgin Islands.
He also said after he appeared on BBC that he was "willing to help any appropriate law enforcement agency with their investigations, if required".
The firm issued the unusual statement after reports in Britain's Sun newspaper and on NBC that USA officials formally requested that Andrew answer questions on the matter.
"These statements were inaccurate, and they should not have been made", Andrew's lawyers added, accusing the DoJ of treating their client "by a lower standard" than anyone else.
A U.S. Federal Bureau of Investigation probe is focusing on British socialite Ghislaine Maxwell, a longtime associate of Epstein's, and others who facilitated his alleged trafficking of underage girls, law enforcement sources told Reuters in December.