The BBC was last night accused of inflicting "deliberate pain" on Prince Harry by dredging up an unfounded slur that he is not Prince Charles's son.
The outrageous and discredited insinuation that Princess Diana's lover James Hewitt is his father is repeated in the controversial BBC2 drama King Charles III, to be screened this week.
The timing is especially cruel so close to the 20th anniversary of Diana's death, and those close to the Royal Family say the hurtful claims should never have been included in a BBC programme, the Daily Mail reported.
Diana's closest confidante, Rosa Monckton, said: "The BBC is deliberately causing pain to a real living person in a salacious fashion. Prince Harry was 12 when his mother died and she is no longer around to reassure him.
I don't think this is why millions pay their licence fee."
Former cavalry officer Hewitt has point-blank rejected the rumours, which "greatly angered" Diana herself, according to her former police bodyguard Ken Wharfe.
Penny Junor, author of an acclaimed biography of Harry, added: "It is irresponsible of the BBC to broadcast this claim."
The new revelation adds to a growing furore over King Charles III, which will be shown on Wednesday.
An adaptation of Mike Bartlett's West End play, it imagines the reign of Prince Charles after he ascends to the throne.
In an early scene in the controversial drama, Harry's friends introduce him to a commoner called Jess as a potential romantic interest.
She asks him: "Is Charles really your dad? Or was it the other one?"
Noticing his "very ginger" hair, she adds: "Cos if Hewlitt [sic] was your dad instead, you would be out the family."
The fictional Harry remains silent, while one of his friends corrects Jess on the name, pointing out that it is Hewitt.
A second friend emphatically denies the rumour.
Harry is played by actor Richard Goulding, who also portrayed the Prince in Channel 4's recent comedy The Windsors.
In Charles III, he depicts Harry as being desperate to rid himself of his Royal title and instead "live a life of normalcy".
He refers to himself as "a ginger joke", "bereft of value" and "clownish", and ushers his friends away.
He and Jess begin a relationship and, towards the end of the drama, he briefly rescinds his title to live a normal life with her, before William takes the throne and Harry resumes his Royal duty.
The reference to Hewitt, who was labelled a "cad" over his affair with Diana, is not the only aspect of the play which could wound the princes.
Tim Pigott-Smith, who played Charles, admitted in an interview before his death last month that the inclusion of Princess Diana's ghost in the 90-minute drama would be "agonising" for her sons.
The actor revealed he found the "hyper-sensitive" scene, in which she appears to her former husband, "incredibly painful" to perform "just because that whole incident was so terrible".
But he insisted: "I don't think it is presumptuous of us to do it or wrong of us to do it. For Charles or William or Harry it would be agonising to watch. That upsets me. But I don't think we've done anything unreasonable or cruel."
Last month, Harry disclosed the anguish he felt after the death of his mother in the 1997 Paris car crash, saying that he sought counselling after he "shut down all his emotions".
Senior Tory Sir Nicholas Soames, a friend of Prince Charles, said: "From what I've heard, this drama is repulsive rubbish and I do not intend to watch it."
Fellow Tory Jacob Rees-Mogg said: "I am sorry that the BBC plans to demean itself by such mean-minded slurs."
The hurtful "Harry-Hewitt" rumour, which has surfaced frequently, is based on little more than the fact that both men have red hair. But it is also a trait of the Spencers, Diana's family. The slur has been comprehensively dismissed by Royal watchers as nonsense.
It is well documented that Diana did not meet the former Life Guards officer Hewitt until two years after Harry's birth in September 1984.
Hewitt, who was mentioned in dispatches when he commanded a Challenger tank in the 1991 Gulf War, had an affair with Diana between 1986 and 1991.
Diana famously told Panorama in her bombshell 1995 interview: "Yes, I adored him. Yes, I was in love with him. But I was very let down."
Hewitt has claimed he considered suicide after his affair with Diana ended.
He once said: 'I got in my car and loaded a few things up to get on the ferry to go to France - to shoot myself ...
"And then my mother insisted on coming with me. And if she hadn't, I would have probably shot myself. So I owe her my life, really."
In an interview with Australian broadcaster Channel 7 recently, Hewitt was asked directly if he was Prince Harry's father and replied: "No, I'm not." He added: "It's worse for him, probably, poor chap."
Ms Junor added: "The claim is absolute nonsense. James Hewitt himself has said it's nonsense. You can't get more conclusive than that. It is irresponsible of the BBC to broadcast this claim.
"I think it's unfair to Harry, the Prince of Wales and James Hewitt to have a public broadcaster peddle this myth.
"The fact is this not a harmless myth - these people are still alive."
Writer and broadcaster Hugo Vickers agreed, saying: "This claim is absolutely ridiculous. I think it's in extremely bad taste for the BBC to peddle this sort of thing and I don't know how they can think they can get away with it.
"It's unpleasant of them to highlight something they know to be untrue. The BBC has no evidence to substantiate this claim and, what's more, they know it has no evidence."
Royal biographer Margaret Holder stressed the claim should have been edited out of the film. She said: "It's nonsense and an urban myth. It has caused a lot of embarrassment and upset for the Prince and the rest of the family.
"The BBC is stirring up an old story which is false and which is going to cause offence to Prince Harry, Prince Charles and the memory of the Princess of Wales.
"The Corporation has editorial control and it should have exercised it to remove this claim."
Asked about the possible upset, a BBC spokesman said: "King Charles III is a BBC2 drama of an award-winning, critically acclaimed, and fictional play."
Buckingham Palace declined to comment last night.