Ashton Kutcher doesn't feel bad about kissing his co-stars, because he wouldn't cheat in real life.

The actor - who can be seen locking lips with Jennifer Garner in romantic comedy 'Valentine's Day' - said his wife, Demi Moore, doesn't mind if he has steamy scenes with other women on camera, because she knows he wouldn't pursue them off-screen.

Ashton explained: "I kiss Jennifer Garner in this one, but we already kissed each other in 'Dude, Where's My Car?'

"If you watch someone kill someone in a movie, you don't think they're an actual murderer. You don't think, 'Oh my God, Robert De Niro's a murderer. Look what he's doing in Taxi Driver!'"

Demi is even so trusting of her partner she was comfortable with him filming graphic full nude scenes with Anne Heche for the film 'Spread'.

'Valentine's Day' features an A-list cast who portray a group of loosely-related characters all preparing to celebrate the romantic day.

Ashton said he was drawn to film because he believes the power love generates can be "shocking".

He told the Metro newspaper: "The line 'Love is the only shocking act' is what made me want to do this movie. Ask everyone if the world could be destroyed in a second and 99 per cent of people will say 'yes'. Ask if world peace is achievable in 50 years and maybe nine per cent will give the same response. The cause of peace is love and when two people really connect - viscerally - it is shocking every time."