PRINCES William and Harry last night launched a scathing attack on Paul Burrell, the former royal butler, for his ''cold and overt betrayal'' of their mother.

Diana, Princess of Wales, would have been mortified at his revelations this week if she were still alive, the brothers said in a remarkable public intervention.

But Mr Burrell later refused to apologise for his new book and said he was ''saddened'' by the princes' statement.

He said his book, A Royal Duty, was ''nothing more than a tribute'' to Diana and he was ''extremely proud'' of it. He also took a swipe at the royal family, saying no-one contacted him or apologised following the collapse of his Old Bailey trial for theft last year.

Mr Burrell, who worked closely with the princess and claimed she called him her ''rock'', has released a series of claims from the book in the Daily Mirror this week.

In yesterday's excerpts, Mr Burrell says that the princess had a string of nine boyfriends whom she compared to racehorses lined up at the starting gate.

In the statement, Prince William, 21, also speaking on behalf of his 19-year-old brother, who is currently in Australia as part of his gap year, said: ''We cannot believe that Paul, who was entrusted with so much, could abuse his position in such a cold and overt betrayal ... it would mortify our mother if she were alive today.''

The comment was released by Clarence House, where a spokeswoman said it was aimed at drawing a line under Mr Burrell's allegations. ''It's telling Paul Burrell that they've had enough,'' she said.

William and Harry would also be prepared to meet Mr Burrell to discuss the matter, Clarence House said.

Later last night, Mr Burrell read out his statement outside a hotel in Cheshire. Asked whether he would be prepared to meet the princes, Mr Burrell said: ''That is what I've always wanted to do.''

However, in his statement, issued earlier through his publisher, Penguin, Mr Burrell said: ''I am saddened at the statement issued on behalf of Prince William and Prince Harry. Saddened because I know that this book is nothing more than a tribute to their mother.'' He added that when they read the book they would ''think differently''.

He said he had received calls of support from some of Diana's closest friends and added: ''I would also like to point out that, following the collapse of my trial at the Old Bailey last year, no one from the royal family contacted me or said sorry for the unnecessary ordeal myself, my wife, and my sons were put through.''

The Daily Mirror said serialisation would continue, and Penguin confirmed last night that the book would be published across the world on Monday.

Buckingham Palace is considering its legal position on the book and has been sent a copy for inspection.

Earlier this week, Mr Burrell fuelled conspiracy theories surrounding the princess's death by writing that she feared for her life and had written of a plot to tamper with the brakes of her car.

In other extracts, Mr Burrell claimed the Duke of Edinburgh wrote to Diana telling her that he and the Queen ''disapproved'' of the Prince of Wales's affair with Camilla Parker Bowles.

Mr Burrell also said that Earl Spencer, Diana's brother, wrote to his sister expressing concern for her mental health.

The earl has said he was angry the private correspondence had been published, but declined to comment on the princes' statement last night.

princes' statement

'We cannot believe that Paul who was entrusted with so much could abuse his position in such a cold and overt betrayal.

''It is not only deeply painful for the two of us but also for everyone else affected and it would mortify our mother if she were alive today and, if we might say so, we feel we are more able to speak for our mother than Paul.

''We ask Paul please to bring these revelations to an end.''

''I am convinced that when the princes, and everyone else, reads the book in its entirety, they will think differently''