Allegations that Diana, Princess of Wales, was murdered are "unfounded", former Metropolitan Police commissioner Lord Stevens said today.

Unveiling the results of his exhaustive three-year high-profile inquiry into Diana's car crash in Paris, he said he had found nothing to justify further inquiries with members of the Royal Family.

Lord Stevens also dismissed claims Diana was pregnant when she died and was planning to marry Dodi.

Detectives were tasked with examining the persistent conspiracy theories surrounding the Paris car crash, including allegations that the Princess and her lover Dodi Fayed were murdered.

Diana, 36, and 42-year-old Dodi were killed when their Mercedes crashed in the Pont de l'Alma tunnel on August 31 1997.

Dodi's father Mohamed al Fayed, who believes Diana and his son were victims of a plot by the Duke of Edinburgh and the British establishment, dismissed the report as "shocking" today even before it was published.

Harrods owner Mr al Fayed, who was not present as Lord Stevens delivered his conclusions but sent a high-powered legal team, said: "I know deep in my heart that I'm the only person who knows the truth."

Lord Stevens bluntly told reporters at a packed news conference in central London: "This was a tragic accident."

He added: "There was no conspiracy to murder any of the occupants of that car."

Lord Stevens's report said there was no evidence of any link between the Duke of Edinburgh and the Security and Intelligence Service (MI6), a reference to claims by Mohammed al Fayed.

Lord Stevens said Diana "was not engaged and was not about to get engaged".

He added: "Prince William has confirmed to me that his mother had not given him the slightest indication of such plans for the future."

He said his investigation was the largest and most comprehensive survey of the crash scene yet and he was satisfied that no information had been held back.

He confirmed that the Duke of Edinburgh was spoken to as part of the inquiry and that two new eyewitnesses had also been uncovered.