Image copyright Centropolis Entertainment Image caption The film revolves around the 1969 Stonewall riots

A petition to boycott a new film that purports to tell the story of the early days of the LGBT rights movement has reached more than 20,000 signatures.

British actor Jeremy Irvine plays a fictional character who incites the 1969 Stonewall riots in New York which kicked off the US gay rights movement.

But the petition accuses the film, Stonewall, of "whitewashing" history.

"It is time that black and brown transwomyn (sic) and drag queens are recognized for their efforts," it says.

It continues: "From the preview alone, we know that will not be happening. Majority of characters casted are white actors, cis men play the role of transwomyn, and folks who began the riots do not seem to be credited with such revolutionary acts."

Cis refers to the term cisgender, which is an individual whose gender corresponds to their assigned sex at birth.

Image copyright Jeremy Irvine/Instagram Image caption Irvine defended the film saying "it represents almost every race and section of society"

The riots, in June 1969, followed a police raid at the Stonewall Inn, a popular gay hangout for Latino and black transgender protestors such as Sylvia Rivera and Marsha P Johnson, both of whom became prominent activists.

They co-founded the Street Transvestite Action Revolutionaries, a group dedicated to helping homeless young drag queens and trans women of colour.

Much of the anger is directed toward's the film's portrayal of Irvine's white cisgender gay character as a leading light in the movement.

The film's director Roland Emmerich addressed the petition on his Facebook page, saying: "I understand that following the release of our trailer there have been initial concerns about how this character's involvement is portrayed.

"But when this film - which is truly a labour of love for me - finally comes to theatres, audiences will see that it deeply honours the real-life activists who were there [...] and all the brave people who sparked the civil rights movement".

"We are all the same in our struggle for acceptance," he adds.

Irvine himself also defended the film in a post on his Instagram account.

"I saw the movie for the first time last week and can assure you all that it represents almost every race and section of society that was so fundamental to one of the most important civil rights movements in living history," he wrote.

The film is due to be released in September.