There is "no credible evidence" of any SAS involvement in the deaths of Diana, Princess of Wales, and Dodi Fayed, police have said.
In August, Scotland Yard began looking at claims that the couple were murdered by a member of British special forces, but today it ruled out opening a criminal investigation.
The allegation is thought to have been made by the former parents-in-law of an ex-soldier, based on information that he talked about in the past. That information was then was passed to the Metropolitan Police via the Royal Military Police.
Mohamed al Fayed, Dodi's father, was "disappointed" by the outcome and will continue his fight "to establish the truth that they were murdered", his solicitor, Simon McKay, said.
He said: "Mr al Fayed will continue his struggle to reveal the truth about the tragedy in Paris which claimed the lives of his eldest son and Princess Diana."
The Met said officers had conducted a "scoping exercise" to assess the "relevance and credibility" of the information provided, and to decide whether it was sufficient to warrant a reopening of the criminal investigation.
In a statement, it said: "This assessment included taking statements from a number of individuals and reviewing records. As part of the scoping officers were given unprecedented access to Special Forces Directorate records.
"Every reasonable line of inquiry was objectively pursued in order to fully evaluate any potential evidence.
"The final conclusion is that, whilst there is a possibility the alleged comments in relation to the SAS's involvement in the deaths may have been made, there is no credible evidence to support a theory that such claims had any basis in fact.
"Therefore the MPS are satisfied there is no evidential basis upon which to open any criminal investigation or to refer the matter back to HM Coroner."
But Mr McKay branded the "so-called scoping exercise" "the latest whitewash in a 16-year cover-up".
He added: "The Met should never have been given charge of the case as they had every incentive to return the result we now see. To have done anything else would have called into serious question their own Paget Report of 2007.
"The case of Soldier N should have been rigorously investigated by the Royal Military Police.
"It was wrong to put in charge of the scoping exercise an officer, Philip Easton, who had been an important figure in the Paget investigation, which said the deaths were accidental, a judgment overruled by the jury at the inquests that said that Dodi and Diana had been unlawfully killed.
"Mr al Fayed will continue his fight to establish the truth that they were murdered and is convinced he will succeed in doing so."
Diana, Dodi and chauffeur Henri Paul died after their Mercedes crashed in a Paris tunnel after leaving the Ritz Hotel on the morning of August 31 1997.
The hearing into the deaths of Diana and Dodi lasted more than 90 days, with evidence from around 250 witnesses.
The inquests concluded on April 7 2008, with a jury returning a verdict that the ''People's Princess'' and her boyfriend were unlawfully killed.
After the hearing, the Metropolitan Police said they had spent £8 million on services arising from the inquest and the Operation Paget investigation from 2004 to 2006.
That money includes the cost of the legal team which represented the force's commissioner at the inquest, police protection for the inquest jury and paying for the Paget inquiry, reported to have cost £3.6 million.
Former Met Police commissioner Lord Stevens's Paget investigation was launched in 2004 at the request of Michael Burgess, the Royal Coroner, who was then overseeing the future Diana inquest.
The former top policeman published his report in December 2006, rejecting the murder claims voiced by some, including Mr al Fayed.