Recordings of Princess Diana about to be released blow the lid on her marriage with Prince Charles

The comments made by the princess to her voice coach show Diana poured out her concerns about her life and her failing marriage as she practised for her upcoming bombshell Panorama interview in 1995.

The tapes, never before played in Britain, are being released in a new Channel 4 documentary, one of several produced to mark the death of the 36-year-old princess in a car accident in Paris on August 31, 1997.

News of the planned broadcast comes just hours after Diana’s sons, Prince William and Prince Harry, took part in an emotional tribute to their mother in the form of a 90-minute documentary looking at her life and the legacy of her charity work.

In the documentary screened on ITV, the princes, who were just 15 and 12 when their mother died, flick through leather-bound photo albums and discuss childhood memories, recalling their fun-loving mother hiding sweets in their socks and taking them on holidays to the beach and water park.

The pair, who were visibly emotional and said they had been “too raw’’ to discuss their mother openly before this, said she had tried to give them a normal childhood, and they expressed regret that they had rushed off the phone to continue playing with their cousins the last time she called them, hours before her fatal accident.

RELATED: Prince William says he felt the presence of his mother Diana on his wedding day

Princess Diana Revealed

The planned broadcast of their mother’s voice-coaching tapes is expected to be deeply upsetting for the princes, who also spoke of their mother’s distress at being hunted by the paparazzi and losing her privacy.

The existence of the tapes has been known since 2001, when they were discovered in a police raid at the home of Diana’s former butler, Paul Burrell.

They were broadcast once in America in 2004 but were considered so controversial they were never shown in Britain.

Diana’s voice-coach Peter Settelen has sold the rights to the tapes to Channel 4, which has produced a documentary called Diana: In her Own Words, to be broadcast in the lead-up to the anniversary of her death.

The BBC attempted a similar documentary and paid more than $50,000 to access the tapes — which were never intended for public broadcast — back in 2007, but dropped the proposal after a public backlash.

The ownership of the tapes has been fiercely fought in the courts for years with the Spencer family seeking to take ownership to ensure they were never broadcast.

However they were returned to Mr Settelen in 2004.

In the shaky video recordings, made throughout 1992 and 1993, Diana laments her need to live up to the “fairy princess’’ public image.

She says she met the prince 13 times before they were married and said: “He’d ring me up every day for a week and then he wouldn’t speak to me for three weeks. Very odd.’’

RELATED: The secrets of Princess Diana’s funeral revealed in new documentary

The princess also talks about a sporadic sex life with the heir to the throne, saying ‘’there was never a requirement for it from him.’’

And discussing her husband’s affair with Camilla Parker Bowles, she says she wishes he would just go away with “his woman and never come back.’’

Sources told The Telegraph that the decision to broadcast the tapes came after Prince William and Prince Harry’s decision to discuss their mother more openly made it more acceptable.

“Because the princes are talking about it, it was considered more OK to release it,” the source said.

The spate of publicity around Princess Diana is expected to be damaging to her former husband Prince Charles, who was almost airbrushed from yesterday’s ITV documentary.

Royal biographer Penny Junor said while the documentary was a “love-letter’’ by the princes to their mother, “they could have just said a little soft, kind word about their father’s love.

“I think he might feel justifiably a little bit hurt, sad, that he doesn’t feature. It didn’t need to be much, just a nod to their father’s presence.”