Colin Firth thinks there are a lot of secretly gay actors in Hollywood.

The British star - who recently portrayed homosexual college professor George Falconer in 60s-set film 'A Single Man' - believes the movie industry if full of male actors who are nervous about coming out in case it jeopardises their careers.

He told Parade magazine: "If you're a straight actor who takes on the role of a gay man, it's obviously not the same as being one in this business. I think there are still some constraints against being openly gay. It is to do with whatever sexual taboos are in place. In Hollywood, I know that some actors are far more circumspect about keeping that secret hidden. There are not a lot of openly gay leading men."

The 49-year-old actor had no qualms about playing George because the movie was written so well the storyline became very "accessible".

He explained: "There's sex running all the way through the movie, even though we don't need to see anybody doing it. I think the fact the man I play is open about the fact he is gay is definitely significant. But I think it just reinforces the power of the story, which is about a love between men that has a very accessible, universal quality."