Colin Firth has suggested that there are “invisible boundaries” preventing out gay actors from taking leading roles.

Firth, a straight actor who played a gay man in Tom Ford’s directorial debut A Single Man, said he felt “complicit” in the problem of gay actors losing out on parts.

Speaking at the UK premiere of the film last night, he said: “There might be risks for a gay actor coming out. The politics of that are quite complex, it seems to me.

“If you’re known as a straight guy, playing a gay role, you get rewarded for that. If you’re a gay man and you want to play a straight role, you don’t get cast – and if a gay man wants to play a gay role now, you don’t get cast.

“I think it needs to be addressed and I feel complicit in the problem. I don’t mean to be. I think we should all be allowed to play whoever – but I think there are still some invisible boundaries which are still uncrossable.”

Firth made similar comments in December, when he said that “sexual taboos” in Hollywood were constraining gay actors.

Out gay actor Rupert Everett said in the same month that he would advise ambitious gay actors to stay in the closet.

He said: “The fact is that you could not be, and still cannot be, a 25-year-old homosexual trying to make it in the British film business or the American film business or even the Italian film business.”

Firth has been tipped for an Oscar nomination for his role as gay college professor George Falconer in A Single Man. He won the best actor award for the performance at the Venice Film Festival last year.

Ford, better known as a fashion designer, has said his debut film is about “love and isolation”, rather than being a “gay story”.