Royal courtiers poisoned the minds of Princes William and Harry, former royal butler Paul Burrell has said.
Mr Burrell's book is due out on Monday
The brothers have accused him of a "cold and overt betrayal".
Mr Burrell has been at the centre of a war of words with the Royal Family over his forthcoming book on Princess Diana.
He told the Sunday Times newspaper royal courtiers had poisoned the princes' "little minds" and "dark forces" were monitoring him.
Earlier this week the Daily Mirror newspaper published an extract from Mr Burrell's book saying Diana believed there was a plot to kill her in a car crash.
In a letter allegedly written by the princess 10 months before her death in a Paris car crash, she apparently told him: "This phase in my life is the most dangerous."
Mr Burrell, who said Diana had called him her "rock", also says the Duke of Edinburgh wrote to her to say he and the Queen "disapproved" of the Prince Charles' affair with Camilla Parker Bowles.
Mr Burrell also says Earl Spencer expressed concern for his sister Diana's mental health.
But he told the Sunday Times these revelations were just the "tip of the iceberg".
And more would come out if Diana's name continued to be besmirched.
Calling himself "the keeper of these secrets", Mr Burrell told the
paper: "I know where the boundary is and I do not cross that line.
"Anything I reveal is to illustrate a fact.
"Other books have been rather sad
Mr Burrell and his wife, Maria, returned home to Farndon, Cheshire, on Saturday, after
staying at a nearby hotel with sons, Alex 18, and Nicholas, 16.
Mrs Burrell told the Sunday Mirror her
family had suffered at the hands of senior royal advisers.
"My family went to hell and back and almost lost everything because of
these people," she told the newspaper.
Describing her husband as the "Princess's greatest protector, she said: "What about my boys?
"What about my family?
gave them any consideration when their dad was dragged to court and threatened
with prison when all he did was protect Princess Diana's world."
Mr Burrell was cleared last year of stealing hundreds of items from the late
princess's estate when his trial collapsed following an
intervention by the Queen.
Harrods boss Mohammed Al Fayed told the Sunday Post newspaper he had always been suspicious about the crash, which also claimed the life of his
son, Dodi, because Diana had told him she feared her life was in danger.
In a statement on Friday the princes made a plea to Mr Burrell to bring these revelations to an end.
A spokeswoman for Clarence House said the princes would be prepared to meet Mr Burrell privately .
And he said he would be prepared to meet them.
Buckingham Palace is considering its legal position on the book and has been sent a copy for inspection.