A former British special forces member claimed there was an elaborate conspiracy to kill Diana and her boyfriend, Dodi Fayed. Scotland Yard examined the claims and found "no credible evidence" that British special forces were involved in the deaths.
The claims, widely reported in the British media, were made by an ex-special forces member identified only as "Soldier N."
"Every reasonable line of inquiry was objectively pursued in order to fully evaluate any potential evidence," police said in a statement Tuesday. "There is no credible evidence to support a theory that such claims had any basis in fact."
Diana, Dodi and driver Henri Paul died when they struck a concrete pier at high speed in an underpass in Paris on August 31, 1997.
A jury for the inquest into the deaths of Diana and Dodi Fayed returned a verdict in April 2008 saying they were unlawfully killed, saying the car's driver and paparazzi share blame for the deaths.
Mohamed al Fayed, Fayed's father, had accused Prince Philip, the queen's husband, of directing a complicated conspiracy that resulted in the couple's car crashing in Paris.
The Associated Press contributed to this report.