Former magazine editor Tina Brown sparked fury by claiming Diana had never been in love with film producer Dodi Fayed.
Ms Brown is understood to have been paid £1million for a book which tells how she became a friend and confidante of the Princess.
However, in what will be seen as an astonishing betrayal, the glamorous socialite claims Diana’s relationship with Dodi was a fling designed to annoy Buckingham Palace.
Last night, Dodi’s father Mohamed Al Fayed hit out at the claims to be published in the run-up to the 10th anniversary of the pair’s death in a Paris car crash.
He pointed to a wealth of evidence which proved the couple were in love and planning to marry.

The Harrods owner dismissed Ms Brown’s book The Diana Chronicles as a “cynical and disgraceful” attempt to make money out of falsehoods.
“This is a total disgrace,” he said. “She is making money – a lot of money – telling stories which are not true.
“Princess Diana and Dodi were in love and planning to spend the rest of their lives together.
“You could see it in their faces and hear it in their voices and we have seen all the other evidence to prove it.”

Mr Al Fayed, who believes Diana and Dodi were murdered in a conspiracy orchestrated by the Royal Family, said:
“Why do people keep saying these things? We have been through it all before and it is just a cynical way of making a profit.
“This is just part of the campaign against me and against everybody who loved Diana. I will carry on until we get to the truth.”
Last year, a Daily Express investigation revealed that the couple died when their heady love affair was at its peak.
Diana had chosen a £130,000 emerald and diamond engagement ring to cement their relationship and they planned to live together in a £4million clifftop mansion in Malibu, California.
They had been planning to announce their engagement to the world the day after the car crash which killed them both, together with driver Henri Paul.
That version of the story was backed up by Monte Carlo-based jeweller Alberto Repossi, who passed his evidence to the police.
Mr Repossi said he had been called to a meeting with Diana and Dodi in the South of France in August 1997, shortly before the smash in the Pont de l’Alma tunnel in Paris.
He said they had seen the ring in his shop window and chosen it. They had made arrangements for Dodi to collect it a week later at the Paris branch of his store.
The jeweller said in a sworn statement, with video and documentary evidence to back him up, that the ring was bought to mark their engagement to be announced shortly afterwards.
Ms Brown, who has edited Vanity Fair and is married to Sir Harold Evans, ex-editor of the Times newspaper, was a regular lunch partner of Diana.
Her book – said to be based on her own memories of the Princess and interviews with a number of “friends” – is being published to mark the 10th anniversary of Diana’s death.
She is believed to have been paid an advance of £1million on sales which are expected to make it a bestseller.
However, friends and supporters of Diana are bound to be dismayed by the allegations about a woman who has been dead for 10 years and cannot defend herself.
Ms Brown claims that, in the weeks that Diana was enjoying a whirlwind romance with Dodi, she was “on the look-out” for a rich, new husband, preferably one with his own private executive jet.
While William and Harry were with the Royal Family at Balmoral, their mother was on holiday with Dodi, spending much of the time aboard his father’s yacht Jonikal off the south of France.
Ms Brown writes: “In August of 1997, Diana was seeking to replace what she had possessed as a Princess with a superstar’s version of the same. What she was really seeking was a guy with a Gulfstream.”
She claims the relationship with Dodi was sparked partly by him ­lavishing expensive gifts on Diana.
She says the Princess also wanted to upset the Royals by having a relationship with someone they would not approve of – a Muslim.
Lord Palumbo, a friend of Diana, told Ms Brown: “She just wanted to make the people at Balmoral as angry as possible.”
The book even claims Diana went behind Dodi’s back and tried to attract Teddy Forstmann, an American millionaire, and Gulu Lalvani, a Hong Kong-based businessman.
Ms Brown accuses Diana of being a liar and a scheming trouble-maker who targeted Prince Charles because of his position as heir to the throne instead of love.
She alleged Diana made up a story that she had tried to commit suicide in a cynical ploy to gain public sympathy.
The book claims to be authoritative, and is said to be based on interviews with more than 250 people, including Tony Blair.
A source said: “It is going to be highly controversial but this book isn’t based on the myths that Diana created about herself and it certainly isn’t gossip.
“Diana was a humanitarian who, at one level, really identified with the common people, as she thought of them, but she was also a very messed-up woman whose downfall was due to her own insane jealousy and self-obsession.”