Police are urging people receiving an email about supposed 'car-jackings' to delete it rather than forwarding it to friends and family as the email is an urban myth.

It has been doing the rounds for some time and police say it appears to be experiencing another circulation surge, after gaining momentum earlier this year when a police employee got sucked in and sent it on with the police logo, lending it credibility.

The email warns that people are being lured out of their vehicle by a piece of paper stuck to the rear window. When the driver leaves the running vehicle to remove the paper, thieves move in and take off with the vehicle.

Police say it is easy for people to be taken in by such stories, evidenced by the fact a police employee saw fit to forward the email on in the first place. They say it is simply good practice not exit a vehicle with keys in the ignition, the engine running and valuables inside.