Guy Ritchie's plans for a 'Sherlock Holmes' sequel are in jeopardy after Robert Downey Jr. claimed the character could be portrayed as gay.

Andrea Plunket, who holds the US copyright to Sir Arthur Conan Doyle's literary creation, is unhappy with comments made by Downey that Holmes and his sidekick Dr. Watson could be lovers.

And Plunkett says if Ritchie and the screenwriters want to take the character - who is played by Downey in the current movie - in that direction she will not allow a follow-up film.

She said: "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."

Plunket's worries were sparked after Downey said in an interview with US talk show host David Letterman that Sherlock could be considered a "butch homosexual".

It is not the first time Downey has spoken about the implied "bromance" between Holmes and Watson - who is played by Jude Law.

He said: "I think the word bromance is so passe. We are two men who happen to be roommates who wrestle a lot and share a bed."