A gaping flaw in keyless cars' security systems has been exposed by high-tech thieves who are using advanced equipment to break into vehicles.
Radio transmitters are being held against the walls of houses to amplify the signal coming from any key fobs that are inside and unlock the car.
The new information comes just days after CCTV footage appeared to show two men unlocking entry to a 35,000 Mercedes using a laptop, hidden in a satchel.
Concerns have been made to manufacturers byThatcham, the British motor insurance industrys research body, after further reports in Britain of these types of crime, which are already commonplace in Europe, according to the Times.
Last year, German researches hacked into 24 different makes of keyless vehicle, including Audis, Fords, BMWs, Citroens and Toyotas using radio devices.
The Mercedes' owner, estate agent Paige Foster, claims brazen thieves used a laptop to hack the keys to her Mercedes from outside her home before driving off in the 35,000 car.
Ms Foster was horrified to discover her partner's nearly new vehicle had disappeared from outside her home in Grays, Essex last week.
CCTV from outside her home shows two men apparently holding up a satchel containing a laptop to gain entry to the car.
In the footage, a hooded figure is seen walking round to the driver's side of the Mercedes while another holds the satchel up against the wall.
The car's door then opens and one of the pair drives it away - despite the vehicle's keys remaining on Ms Foster's kitchen table.
The 23-year-old believes the theft of her and partner Richard Haydon's car was done to order and says the incident has left her fearing for her safety.
She said: 'When I saw the video it made me feel sick - these people know where I live, they have obviously followed me or looked me up to find the car.
'The CCTV shows them walk round the back so they can't be seen by the cameras - they just pop up at my car.
'It looks like the guy up against the house has an iPad or a laptop in the leather satchel which contains the device that picks up the signal - it looks like they can decode the key to open the car.
'We have been told it's some sort of Russian military software.
'When I saw the footage I burst into tears. The fact that someone was watching me and took it not even a metre away from the front of the house is awful.'
She added: 'One of the men drove off in the car while the other, the one with the satchel, walked off - he might have been walking to his own car which could have been parked up on the estate.'
Ms Foster reported the incident to the police and contacted her insurance company who flagged that an HPI vehicle background check had been run on the car on April 5 - six days before the Mercedes vanished.
She added: 'I've heard that other vehicles have been taken from the area - two weeks ago another Mercedes and a Range Rover was taken.'
She is now sharing the CCTV footage in a bid to catch the culprits and to warn others about the hack it appears thieves can carry out.
Paige said: 'Cars that have the Keyless Go system don't need the key to start the engine - it just needs to be within a certain distance, it's usually in my pocket.
'The night the car was taken the key was stored in the back of the house, not in the hallway near the front door.
'I would try to avoid the keyless system in future and would strongly recommend people to look into the fob guard which protects the car's wireless system.
'Mercedes have been really helpful, they've tried to track the car down using the tracker but it looks like it's been deactivated.'
A Mercedes-Benz spokesperson said: 'We're sorry to learn about this customer's experience but we're not aware of any complaints resulting from theft related to keyless entry/start systems on Mercedes-Benz cars.
'All Mercedes-Benz vehicles have extensive security and anti-theft protection systems. Data security, data protection and anti-theft protection are important elements in our research and development activities.
'The development of protection and safety mechanisms is continued over the entire life cycle of a vehicle.
'When enhancing our protective mechanisms we take into account the latest knowledge about criminal methods and about attacks on security systems.
'We also offer our customers the option of deactivating the radio signal with two clicks of the key in order to prevent abuse.'
Essex Police confirmed they were looking into the incident.
An Essex Police spokesman said: 'Police are investigating the theft of a car from an address in Grays.
'A black Mercedes Benz C220 was taken by two men between 10pm, Monday, April 10 and 9am Tuesday, April 11.
'The first suspect is described as being of large build and between 5ft5in and 6ft. He was wearing jeans and a black hooded top.
'The second suspect is described as being of skinny build and around 5ft5in tall. He was wearing jeans with a grey body warmer jacket.'