Prince William and Prince Harry have expressed regret at the publication in Italy of a picture of their mother Princess Diana in the wreckage of the car crash that took her life.

"We feel deeply saddened that such a low has been reached," William and Harry said in a statement issued by Clarence House, the official London residence of their father Prince Charles on Friday.

"Despite the support shown to us and our mothers 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."

Chi, a weekly newsmagazine in Italy, has published the image of Diana being given oxygen at the scene of the crash in a Paris road tunnel in August 1997 that took her life and those of her lover Dodi Fayed and driver Henri Paul.

Umberto Brindani, Chi's editor, has said the photo comes from a just-published book in France by crime writer Jean-Michel Caradec'h, titled "Lady Diana: The Criminal Investigation".

William and Harry, who have both embarked on military careers, urged other publications to refrain from reprinting the photo.

"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 mothers family and all those who so loved and respected her," they said.

Britain's domestic Press Association news agency quoted Brindani as saying that the photo -- under the headline "World Exclusive: The Last Photo" -- was "touching" and "tender", and not offensive.

"I published the picture for a very simple reason -- it has never been seen before," the editor said. "In my opinion it is not a picture which is offensive to the memory of Princess Diana."

Caradec'h's book is said to also include photos of Diana taken shortly after the high-speed car crash inside the Pont d'Alma underpass, as well as autopsy diagrams detailing the extent of her injuries.