Diana's family lead backlash against Channel 4 documentary revealing intimate sex life with Prince Charles

Earl Spencer reportedly pleads with Channel 4 not to screen the tapes because of their effect on Prince William and Prince Harry

Intimate details about Diana's sex life with Prince Charles are recorded on the tapes (Getty)

Channel 4 is facing strong backlash from Princess Diana’s family and friends after the broadcaster announced it is going ahead in screening a new documentary revealing the intimate relationship and sex life between her and Prince Charles.

Due to be aired to mark the 20th anniversary of her death on 31 August 1997, it features previously unseen footage of Diana speaking to her voice coach, Peter Settelen.

She can be seen laying bare details about their sex life and, at one point, she claimed that her husband had said it was in his right to have a “mistress”.

She said that the pair had sex “once every three weeks” but that it fizzled a few years after Prince Harry was born in 1984.

Diana also confessed having found solace with her married protection officer Barry Mannakee, a relationship she suggested was not sexual but that she had considered fleeing the Royal household for.

She said she felt “deeply in love” with him and when he later died, she described the moment as “the biggest blow of my life”.

Describing the moment she confronted the future king about his relationship with Camilla Parker Bowles, she said that Prince Charles told her he refused “to be the only Prince of Wales who never had a mistress”.

She also claimed that the Duke of Edinburgh told his son that he could have an affair with Camilla if his marriage had failed after a set period.

“My father-in law said to my husband, ‘If your marriage doesn’t work out, you can always go back to her after five years,’” she said.

Diana also revealed that she approached the Queen, described as “the top lady”, for advice.

“I went to the top lady, sobbing,” she explains in the tape. “I said, ‘What do I do. I’m coming to you, what do I do? And she said, ‘I don’t know what you should do. Charles is hopeless’. And that was it, that was help,” she adds.

The footage was recorded by Mr Settelen, who helped the princess with her public speaking between 1992 and 1993.

They were returned to him after a lengthy dispute with Diana’s family, headed by her brother Earl Spencer, who said the footage belonged to them.

He has now pleaded with Channel 4 not to broadcast the footage, which he told the Mail on Sunday would cause distress – particularly to Prince William and Prince Harry.

One of Diana’s closest friends, Rosa Monckton, also told the paper: “How intrusive is this? It doesn’t matter that it was 20-odd years ago. The tapes should have been sent to the boys. I just think it is absolutely disgusting.”

The programme called Diana: In Her Own Words will be broadcast on 6 August and uses some of the tapes to reveal private details about married life between the Prince and Princess of Wales, from the perspective of Diana.

Footage taken from the tapes has already been shown in a documentary broadcast in the US 13 years ago, but it was never screened in the UK.

Other friends of the Royal family are reportedly horrified about the broadcasting of the tapes, calling Channel 4’s decision “exploitative” and “ghoulish”.

Penny Junor, the Royal biographer who has previously written about the Prince of Wales, the Duchess of Cornwall, Prince William and Prince Harry also condemned the decision to broadcast the tapes.

She told The Telegraph that the documentary was “another way of exploiting Diana” and that it was not what either Prince Charles or his children would have wanted.

But Channel 4 defended its decision to go ahead in screening the documentary.

In a statement it said: “The excerpts from the tapes recorded with Peter Settelen have never been shown before on British television and are an important historical source.

“We carefully considered all the material used in the documentary and, though the recordings were made in private, the subjects covered are a matter of public record and provide a unique insight into the preparations Diana undertook to gain a public voice and tell her own personal story, which culminated in her later interview for Panorama.

“This unique portrait of Diana gives her a voice and places it front and centre at a time when the nation will be reflecting on her life and death.”