In the past 28 days Leicestershire Constabulary has received 20 reports of burglaries where car keys and cars have been stolen.
Many of these have taken place at addresses in north of the county and vehicles taken include several BMW 1 series, a Jeep Cherokee and a Saab 93.
Patrols have been increased in the areas affected by the incidents.
Officers would like to hear from anyone who knows who is committing these offences or where the cars are being taken to once they have been stolen.
They are also keen to hear from anyone who sees any suspicious activity in their area, particularly around higher value cars parked on driveways.
Officers are advising people to keep their premises secure at all times, lock all windows and doors and ensure all keys are kept out of sight and in a secure place.
Anyone with information is asked to contact Crimestoppers, anonymously, on 0800 555 111.
Incidents have taken place in Long Whatton, Oakham, Ashby, Ravenstone, Lockington, Castle Donington, Newbold Verdon, Earl Shilton, Burbage, Market Bosworth, Burton on the Wolds, Quorn, Anstey, Cropston and Leicester Forest East.