The US copyright holder of the Sherlock Holmes series has threatened to withdraw permission for a film sequel if producers develop a homoerotic storyline.

Sherlock Holmes was released in the UK on Boxing Day. It stars Robert Downey Jr as the famous detective and Jude Law as his sidekick, Dr Watson.

In interviews, Downey Jr has discussed the homoerotic tension between the two characters, who are shown wrestling and sharing a bed.

He recently told chatshow host David Letterman that he wondered whether Holmes was “a very butch homosexual”.

However, the US copyright holder, Andrea, Plunkett, has threatened to withdraw permission for a sequel if Holmes and Watson become gayer.

She told Total Film: “I hope this is just an example of Mr Downey’s black sense of humour. It would be drastic, but I would withdraw permission for more films to be made if they feel that is a theme they wish to bring out in the future.

“I am not hostile to homosexuals, but I am to anyone who is not true to the spirit of the books.”

Before the film’s release, one critic warned that the gay twist could turn cinema audiences off.

Former New York Post critic Michael Medved, who is a self-proclaimed conservative and famous for adding a family suitability rating to his film reviews, said: “They know that making Holmes and Watson homosexual will take away two-thirds of their box office.

“Who is going to want to see Downey Jr and Law make out? I don’t think it would be appealing to women. Straight men don’t want to see it.”

Sherlock Holmes is currently faring well in both the UK and US box offices, coming in at second behind Avatar.