James McAvoy's humour became ''way more filthy'' after filming 'Filth'.

The 34-year-old actor - who is married to Anne-Marie Duff - plays corrupt police officer Bruce Robertson in John S. Baird's big screen adaptation of Irvine Welsh's twisted novel of the same name, and the dark comedy rubbed off on him.

He told Nuts magazine: ''My sense of humour did become way more filthy and it's already filthy. My wife did start to get a bit like 'This is getting a bit too much mate.' I went home very tired because it took a lot of energy.

''Weirdly, this character came a lot more naturally for me than a lot of parts I've played, probably because even though the film is so surreal, he's still someone I believed wholeheartedly in.''

Although 'Filth' is a far cry from the frothy romances he has previously starred in, he would still gladly be cast in another rom com.

Quizzed on whether he would take on any more romantic roles he said: ''I think so. I like romantic stuff asnd I haven't done much in a while. When I read a script, I don't think 'Is this film funny and touching or dark and less loving?' The important criteria is, is it good? If something romantic comes in that's interesting, why not?''