US censors have once again been accused of homophobia after British drama Pride was hit with a restrictive rating.

The Motion Picture Association of America (MPAA) handed the Cannes film festival hit an R rating, which means no one under the age of 17 can legally view it without a parent or guardian. The move prompted fury from campaigners and fans of Matthew Warchus’s film, which tells how gay and lesbian activists threw their support behind a Welsh mining community during the strike of 1984. “It is outrageous, knee-jerk homophobia,” said Peter Tatchell. “There’s no significant sex or violence in Pride to justify strong ratings. The American classification board seems to automatically view any film with even the mildest gay content as unfit for people under 17.”

In August the MPAA came under fire after Love is Strange, a film about two older gay men which features no sex, nudity or violence, was handed a the same restrictive R rating.

Pride, which stars Imelda Staunton and Bill Nighy, features only one mild instance of explicit imagery when a group of women find some gay porn magazines in a bedroom. The British Board of Film Classification gave the film a 15 rating, citing the above scene and one showing a gay club in which men wear bondage-style clothing, as well as “occasional strong language” for its decision.

The body has not given any public comment on its reasons for the move.

Pride, which won the Queer Palm award at this year’s Cannes film festival, was released in UK cinemas last month. It received a limited release in US cinemas last weekend.

• This article was amended on 2 October, as the original said the film had been given an NC17 rating, rather than an R.