Number plates have been stolen from 48 cars in the Swindon area in the past six months, police have revealed.
The thefts have occurred in both residential and industrial areas.
Detectives believe the plates are being taken as souvenirs or to clone a car's identity for criminal purposes.
Motorists are being urged to consider measures to safeguard their plates, such as using clutch-head screws which cannot be removed with standard tools.
Det Cons Steve Caskey said: "Thieves target number plates for a variety of reasons including for fun 'trophies' or in more serious cases to clone the identity of another vehicle for use in crime.
"It is a nationwide problem and whilst motorists in Swindon are not especially at high risk, these offences are occurring at times and locations that means no one area is more likely to be targeted over another."
Other precautionary measures include buying a new type of number plate that shatters if anyone tries to remove them and parking in busy, well-lit areas.