Panorama’s investigation into sex allegations surrounding the Duke of York has been described by one royal writer as “about as bad as it gets for Andrew”.

Penny Junor said the duke’s accuser, Virginia Giuffre, came across as a more sympathetic character compared with his own Newsnight interview.

But she warned there was no way to know which one was telling the truth.

Ms Giuffre, in the interview on BBC One on Monday evening, claimed she was trafficked by since-disgraced financier Jeffrey Epstein and forced to have sex with Andrew when she was a teenager, which the duke categorically denies.

She said Andrew was “the most hideous dancer I’ve ever seen in my life” and “his sweat was … raining basically everywhere”.

Ms Giuffre added: “This is not some sordid sex story. This is a story of being trafficked, this is a story of abuse and this is a story of your guys’ royalty.”

Ms Junor told the PA news agency: “This is about as bad as it gets for Andrew.

“Virginia Giuffre sounds very plausible in this interview, while most of Andrew’s excuses in his interview with Emily Maitlis were laughable.

“She also comes across as a much more sympathetic character so viewers will warm to her.

“This made gruelling watching and the stories these girls tell are terrifying.

“Jeffrey Epstein was a monster and if what the girls say about (socialite) Ghislaine Maxwell is true, then she was no better. Whether Andrew actually slept with Virginia Giuffre I think is still unproven.”

Ms Junor warned: “Virginia Giuffre is absolutely right that only one of them is telling the truth, but we still have no way of knowing which of them it is, and I think we should be cautious about which one we choose to believe. That has to be left to the FBI.”

Graham Smith of Republic, which campaigns for an elected head of state, said: “This interview is likely to be hugely damaging to Andrew and the royal family.

“The Queen and Charles have known about these accusations for eight years and did nothing until it became a PR disaster.

“Still the royals hide behind palace gates denying the allegations but refusing to do anything that might help law enforcement or alleged trafficking victims in the US and the UK.”

Mr Smith called on the duke to be properly investigated by British police.

“To hear that Giuffre made a complaint directly to the Metropolitan Police, and they did nothing, is scandalous,” he said.

“Are the royals above the law?  Is there any line they might cross that will lead the police to act?

“Any other person in this country, faced with such serious accusations against them, would face investigation by the police, whether the offences took place in the UK or abroad.”

Duke of York
Andrew, pictured with his ex-wife Sarah, stepped down from public duties after his Newsnight interview (Adam Davy/PA)

But Daniel Janner QC warned that the BBC runs the risk of a trial by media of the duke.

The founder of Falsely Accused Individuals for Reform (Fair), which campaigns for anonymity before charge in relation to sexual offences, said: “There is a danger in the Prince Andrew case of assuming guilt by association. He is entitled to the presumption of innocence.

“Those making allegations against Prince Andrew should have their evidence forensically tested to ensure they are not motivated by false compensation claims against a lucrative estate.”

A Buckingham Palace spokesman said in response to the allegations on Panorama: “It is emphatically denied that the Duke of York had any form of sexual contact or relationship with Virginia Roberts (Giuffre). Any claim to the contrary is false and without foundation.”

On the duke’s association with Epstein, the palace spokesman added: “The Duke of York unequivocally regrets his ill-judged association with Jeffrey Epstein. Epstein’s suicide left many unanswered questions, particularly for his victims.

“The duke deeply sympathises with those affected who want some form of closure. It is his hope that, in time, they will be able to rebuild their lives.

“The duke is willing to help any appropriate law enforcement agency with their investigations, if required.

“The duke has already stated that he did not see, witness or suspect any behaviour of the sort that subsequently led to Jeffrey Epstein’s arrest and conviction.

“He deplores the exploitation of any human being and would not condone, participate in, or encourage any such behaviour.”