British actor James McAvoy has revealed that he hated the sex scenes between himself and Keira Knightley in new film 'Atonement' - because he found them "sweaty and uncomfortable." The 28-year-old actor, best known for his role in British television show 'Shameless,' recently admitted that he dreaded shooting for the sex scenes with Knightley.Sex scenes are always a nightmare. It's never easy and it's always a little bit sweaty and uncomfortable," the New York Post quoted him, as telling New Zealand's Stuff Web site.

"When they call action, if you feel the lady's breast, it's your decision to feel the lady's breast. It's like, this is wrong. You have no parameters," he added.

Keira, according to the actor, was also just as embarrassed, but the pair apologised to each other afterwards.

"We carried on and about 10 seconds later we just said very sheepishly, 'Sorry about that,'" he said.