Diana, Princess of Wales, was heard today describing the moment she confronted Camilla Parker Bowles about her affair with Charles.

The late Princess made the disclosure in a second round of secretly-recorded tapes, which were aired for the first time in the United States.

On the recordings, made at Kensington Palace in the early 1990s, she also told of her plan to "cut a very different path" from the rest of the Royal Family.

And she said a doctor told her that her bulimia and depression could easily be cured, saying to her: "The problem lies with your husband."

Describing the confrontation with Ms Parker Bowles, which occurred at a birthday party for Mrs Parker Bowles’ sister in 1989, Diana said: "The voice inside me had said ’just go for it’.

"I was terrified of her. I said, ’I know what’s going on between you and Charles and I just want you to know that’."

Diana chose to confront Ms Parker Bowles when she was speaking to the Prince of Wales and another guest.

She said on the tape: "I said to the two men, ’OK, boys, I’m just going to have a quick word with Camilla and I’ll be up in a minute’.

"And they shot upstairs like chickens with no heads and I could feel, upstairs, all hell breaking loose - ’What is she going to do?"

She said Mrs Parker Bowles told her: "You’ve got everything you ever wanted. You’ve got all the men in the world fall in love with you and you’ve got two beautiful children, what more do you want?".

"So I said, ’I want my husband’," Diana said.

"And I said to Camilla, ’I’m sorry I’m in the way... and it must be hell for both of you. But I do know what’s going on. Don’t treat me like an idiot’."

Never-seen-before video footage was also shown on the programme, aired by the US network NBC.

The film was taken by a voice coach when Diana was training for a new, more public, role as a single woman.

During the session, Princes William and Harry, then 11 and nine, came into the room, although they were not seen on tape.

William asked: "Can I watch this?" Diana answered: "You come in here, sit down and watch this." Gesturing to the video camera she said: "Don’t touch it, William, because it’s all focused on me."

Later, when Harry laughed, she said: "Harry, shush. Just sit." William echoed: "Exactly Harry, shush." The coach rehearsed a mock interview with Diana.

Asked why she did charity work, she joked: "Because I’ve got nothing else to do."

William was heard to say: "That’s terrible - it’s recording."

In the end, she said: "I’ve not a clue to that question."

Asked what she would do if she were not the Princess of Wales she said: "I would like to have a role which brought me into contact with every day life and the man on the street - does that sound condescending?"

As she grew tired, she said she was "knackered" and could not go on with the session.

Most of the tapes were recorded secretly by Diana and smuggled out of Kensington palace by a friend, Dr James Colthurst.

With Diana’s approval, he passed them to Andrew Morton to form the basis of his bestseller, Diana: Her True Story.

On the latest tapes to be broadcast she told how a friend gave her the ultimatum - that she would expose her bulimia in the media unless Diana sought help.

"I suddenly woke up and realised that I was on the way down fast," she said.

She spoke to a doctor: "He said: ’how many times have you tried to get rid of yourself?’ and I thought, ’Wow’. I said about four or five times," Diana said.

She went on: "He said ’I can get you better in no time at all. The problem lies with your husband’. And he said ’in six months time you’ll be a totally different person’."

During her interview training she told how she planned to break ranks from the Royal Family.

"I think I am going to cut a very different path to everyone else, for everyone else. I am going to break away from this set-up and go and help the man on the street."

Diana said she was "looking forward to it". She said she would prove to the world that she could "jolly well fulfil this position".

Asked how she saw her role in five years time she said: "I haven’t a clue to that question." Within five years she was dead.

She added: "I had so many dreams as a young girl - hopes that my husband would look after me and be like a father figure, he’d support me, he’d care for me... I didn’t get any of that."

The documentary detailed how Morton’s book was put together.

Dr Colthurst said he passed drafts of Morton’s manuscript for her to edit. She made changes, for example altering Morton’s words that she "longed to marry" Charles, to "was in love with".

Morton and Dr Colthurst both recounted how nervous Diana was when the book was about to be serialised in a newspaper.

Diana wrote to Dr Colthurst that she was "preparing for the volcano to erupt".

"Morton said Diana was "very nervous", adding that she had "severe second thoughts".

In the first round of tapes, aired last week, Diana detailed apparent attempts at suicide by hurling herself down a flight of stairs, slashing her chest and thighs with a penknife, cutting her wrists and throwing herself into a glass cabinet at Kensington Palace.

She said the Prince of Wales made her "feel so inadequate in every possible way".

She claimed Charles had been disappointed that their second child, Harry, was a boy and that he hated his red hair.

She also claimed that she had wanted Prince William’s birth to be induced - but had to schedule the procedure around her husband’s polo games.

"My husband made me feel so inadequate in every possible way that each time I came up for air he pushed me down again," she said.

NBC said the tapes were recorded between September 1992 and December 1993, at a time when Diana’s marriage was in turmoil. The marriage came to an end in July 1996.