Their comments come after UK magazine distributors were urged not to import copies of the Italian magazine Chi.

In a statement, the princes said they were upset that "such a low has been reached" adding they would make moves to protect her, as she had them.

UK newspapers have condemned Chi but its editor says the photo is "tender".

Princess Diana and Dodi Al Fayed died on 31 August 1997

The princes' statement said: "Despite the support shown to us and our mother's memory by so many people over the last eight years, we feel that as her sons we would be failing in our duty to her now if we did not protect her as she once did us.

"Therefore we appeal to all forms of media throughout the world to appreciate fully that publishing such material causes great hurt to us, our father, our mother's family and all those who so loved and respected her."

'Touching, tender'

Mohamed Al Fayed, whose son Dodi was also killed in the 1997 car crash, also condemned the "vile publication" of the picture.

But Chi's editor Umberto Brindani said the picture was "touching" and "tender".

The photograph shows the princess being given oxygen in the wreckage of the Mercedes car in which she died.

British newspapers have always refused to publish the picture.

Under the headline "world exclusive - the last photo" it has been published in Chi and reproduced in an Italian newspaper.

It makes me sad and angry that a magazine would reproduce an image of the Princess as she clung desperately to life  Mohamed Al Fayed

In Chi, it accompanies an article about a forthcoming book which examines the criminal investigation into Diana's death.

Mr Al Fayed said the publication of the photos represented a "heartless pursuit of money".

"It makes me sad and angry that a magazine would reproduce an image of the princess as she clung desperately to life," he said.

"The editor and the author, who probably have families of their own, have no thought for the feelings of those who loved the princess, first and foremost her sons, Princes William and Harry."

Chi editor Umberto Brindani said he had published the picture for the "very simple reason" that it has never been seen before.

"In my opinion it is not a picture which is offensive to the memory of Princess Diana," he added.