Image caption Oscar-nominated actress Naomi Watts plays Princess Diana in the film

The director of Diana says he has "no regrets", despite the film's poor reception in the UK.

Oliver Hirschbiegel told the BBC that the movie's critical mauling was "devastating, but when you make a film you don't think about the reactions".

The Telegraph described the film "a special class of awful", while the Mirror called it "cheap and cheerless".

Hirschbiegel admitted the reviews had put off audiences, but he still hoped people would "make their own minds up".

"In all the other places where it's opened - in Poland, the Czech Republic, Turkey and Slovakia - it's been very strong," he said.

"I think for the British, Diana is still a trauma they haven't come to terms with."

Starring Naomi Watts, the film depicts Princess Diana in the final years of her life, with a focus on her affair with heart surgeon Hasnat Khan, played by Lost's Naveen Andrews.

Image caption Oliver Hirschbiegel says his depiction of Diana is "very un-British"

It entered the UK chart at number five in its opening weekend, taking £623,000 at the box office. This week, it dropped to number nine.

Hirschbiegel, who previously made Downfall, a German-language film about the last days of Hitler, called his experiences with Diana "deja vu, because it has the same reactions in the UK as Downfall had in Germany on release".

"I hope it is a matter of stepping back and looking at it afresh in a year or so, because it is a very British story and I am a very German director."

He added that Diana "was the most complex character I have ever tried to depict - more complex than Hitler. The one thing they both had in common was they were born actors".

Earlier this week, at the Zurich Film Festival, Hirschbiegel described the film as "very un-British" and described the critical reaction as harking back "to what newspapers like the Daily Mail would write about her back then - really vile things. So I guess I succeeded."

The film has been sold to distributors in more than 40 countries and will be released in the US on 1 November, 2013.