An investigative journalist, formerly of the reputable Paris Match magazine, claims to have uncovered the explosive proof from archives at the hospital where the Princess was taken after the crash on the night of August 31 1997.
The document has previously remained hidden for 10 years due to “ethical and privacy” concerns, according to respected investigative reporter Chris Lafaille.
The journalist makes the shocking claims in a new book called Diana, the Inquiry They Never Published to coincide with the tenth anniversary of her death later this month.
He said: “It is a near certainty Diana was nine to 10 weeks pregnant at the time she died, according to papers from the Paris Public Hospitals archives.
“The document dated August 31 1997 was sent to the then minister of the interior Jean-Pierre Chevenement, with copies to health minister Bernard Kouchner, foreign affairs minister Hubert Vedrine and Paris police chief Martine Monteil.”
He added: “It has never been claimed or proved to be a fake.”
The revelation would explain why the Princess was illegally embalmed in the hours after her death. The process, carried out contrary to French law, meant any potential pregnancy test results would have been rendered invalid.
The pregnancy claims address one of the key questions set out by the coroner to be answered at the inquest into Diana’s death, which is due to begin in October. Coroner Lord Justice Scott Baker recently listed 20 key issues he intends to explore during up to six months of hearings.