James McAvoy, says sex scenes are a nightmare

Keira Knightley's Atonement costar, James McAvoy, says getting intimate in front of the cameras is never easy, PEOPLE reports .

"It's always a nightmare, isn't it?" he said in a recent television interview. "It's never easy and it's always a little bit sweaty and uncomfortable."

McAvoy, 28, appeared on Britain's Michael Parkinson show to discuss his role in Atonement.

"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 said.

"What was great about Atonement was Joe Wright [the director] was very, very, very on the ball with what he wanted, so when you were doing something it was at his behest."