London (CNN) Lawyers representing alleged victims of convicted sex offender Jeffrey Epstein have threatened to subpoena Prince Andrew after the royal was accused of "zero co-operation" with US prosecutors.

In November, the prince said he was "willing to help any appropriate law enforcement agency" if required, after he appeared in a BBC Newsnight interview in which he was questioned over his friendship with Epstein.

But Geoffrey Berman, US attorney and the lead prosecutor in the inquiry, said Monday that the Duke of York has not responded to requests for an interview.

"It's fair for people to know whether Prince Andrew has followed through with that public commitment," said Berman, the US Attorney for the Southern District of New York.

"To date, Prince Andrew has provided zero cooperation."

Gloria Allred, a US lawyer representing some of Epstein's alleged victims, told BBC Radio 4's Today program on Tuesday: "This is ridiculous. It's just not acceptable."

She added: "I don't now whether Prince Andrew thinks he's above the law or whether he thinks that he doesn't know anything... but excuses just don't cut this anymore."

Lisa Bloom, another US lawyer representing five women who say they were abused by Epstein, told BBC's Newsnight on Monday that her clients were "outraged and disappointed" by Prince Andrew's failure to cooperate.

"If Prince Andrew truly has done nothing wrong then it's incumbent upon him to go and speak to the FBI at a time that's convenient for him and say what he knows," she said. "Perhaps he can help bring other people to justice."

Buckingham Palace did not provide any comment in response to CNN's request.

Can the US subpoena Prince Andrew?

A subpoena is an order that compels someone to appear in court or to submit evidence.

Antonios Tzanakopoulos, associate professor of Public International Law at Oxford University, told CNN that a US court "can always issue a subpoena" but they cannot make someone comply if they are in another jurisdiction, including the UK.

Allred told the BBC that lawyers in the civil lawsuit could seek to subpoena Prince Andrew if he were to travel to the US. "Certainly, if he ever came back to the United States, that would be one of the first things that I'm sure a lot of lawyers, including me, would want to do," she said.

If he were to travel to the US on an official visit, it is likely he would have some form of immunity, although it might be different if he were on a private visit, added Tzanakopoulos.

A photograph appearing to show Prince Andrew with Virginia Roberts Giuffre and, in the background, Ghislaine Maxwell.

Is there another way Prince Andrew could be made to give evidence?

Countries including the UK and US have a Mutual Assistance Treaty , but this is reserved for criminal matters, says Tzanakopoulos. "There is no criminal matter pending in regard to Prince Andrew," he said.

Epstein died by apparent suicide in August, so his alleged victims have instead brought a civil suit against his estate, claiming damages. The FBI's criminal investigation concerns Epstein's alleged co-conspirators.

Virginia Giuffre, one of Epstein's accusers, claims she was trafficked to London by Epstein in 2001, when she was 17, and forced to have sex with his friends, including Prince Andrew.

The prince has emphatically denied any form of sexual contact or relationship with her.

The US could make a request to the UK's High Court under a law that provides assistance in civil matters, says Tzanakopoulos, but this process is "so permissive it's easy to give reasons not to do it."

Are the UK courts likely to help?

The UK makes its own rules on how to comply with a request relating to a proceeding in a foreign court.

The Evidence (Proceedings in Other Jurisdictions) Act 1975 states that "a person shall not be compelled ... to give any evidence if his doing so would be prejudicial to the security of the United Kingdom."

Tzanakopoulos believes that "if we're talking about the Queen's son, arguments could easily be made that it is prejudicial."

Anna Bradshaw, a lawyer at Peters and Peters Solicitors, told CNN that even if a request were made for Mutual Legal Assistance in a criminal case, the prince could respond in a UK court with all the accompanying protections available under UK law.

Even if such a request were granted or refused, Bradshaw said, the public would not necessarily know about it -- UK government policy is not to reveal the details of such requests.