The one-and-a-half minute video has debuted on July 1, 2011 - the day the Princess would have celebrated her 50th birthday.
Unlawful Killing premiered at this year's Cannes. The new trailer seeks to "discredit many of the misconceptions that have surrounded the film prior to and since its screening at the Cannes Film Festival", an official press release states.
Watch Digital Spy's world exclusive Unlawful Killing trailer below:
The documentary will mix interviews with recreations of the official inquest into the Paris car crash that killed Diana, her boyfriend Dodi Fayed and their driver Henri Paul in August 1997. It includes contributions from the late Tony Curtis, Howard Stern, the film's backer Mohamed Al-Fayed, Piers Morgan and Michael Mansfield QC.
Unlawful Killing has so far secured distribution in Russia, Spain, Belgium, the Netherlands and Luxembourg, with interest from the US, Japan, Italy and Australia.
Director Allen's refusal to censor the film could mean that it never secures a release in the UK, although a potential slot at the London Film Festival has allegedly been discussed.
> Cannes 2011: Keith Allen on his Diana doc Unlawful Killing