Scottish actor GERARD BUTLER is at the centre of a Los Angeles police criminal investigation after allegedly assaulting a photographer.

The P.S. I Love You star was driven off in a waiting limousine after leaving an LA bar at 2am on Tuesday morning when a waiting photographer began to follow the actor's vehicle in his own car.

According to reports, Butler ordered his limousine to stop, before climbing out and asking the unnamed snapper why he was being followed.

When the man responded, "Hey, that's my job," Butler allegedly reached in the car, grabbed the photographer's throat and punched him with a closed fist.

According to reports, the paparazzo had to be treated in hospital for his injuries, which were stitched up before he went to file a police report for the incident.

Officials at the Los Angeles Police Department have confirmed they are looking into the case and plan on interviewing the actor.