Motor insurance premiums in the Wirral are rocketing because gangs of joyriders are stealing luxury vehicles by hooking keys through letterboxes.
Wirral police are cracking down on thieves who have stolen more than £500,000 worth of luxury cars from homes in the area.
Gangs of youths, mainly from Liverpool, are stealing an average of 15 high performance cars, such as Mercedes and BMWs, each month.
The method of theft involves a cane, stick or extended metal bar being placed through the letterbox of homes. This either has a hook or magnet on the end which is used to remove the keys.
According to a Wirral insurance broker, motor insurance premiums in the most severely hit areas, Bromborough, Bebington and Meols, have increased by up to 15%.
Detective Inspector Colin Leeman said a "significant number" of arrests have been made in relation to the crimes.
Almost every car stolen since April has been recovered, but most have been found burnt out or crashed.
MMA claims service and operations manager Bob Still said this type of car crime was becoming more common. He added insurers were often too slow in warning customers about the dangers of crime.
"If we are to keep premiums down, we need to warn customers to keep keys away from doors, perhaps by starting a national campaign," he said.