Four of the UK's five best-selling cars are "susceptible to keyless theft", it has been claimed.
Consumer group Which? said Ford Fiesta, Volkswagen Golf, Nissan Qashqai and Ford Focus models were at risk.
The other car in the top five sellers - the Vauxhall Corsa - was considered to be safe from attacks as it does not feature keyless entry and start.
Which? based its report on data from the General German Automobile Club (ADAC), a roadside recovery organisation, which saw 237 keyless cars tested and found that all but three of them are susceptible to so-called relay attacks.
Relay attacks see criminals use a device to trick a car into thinking a key is within close enough range to be opened and the ignition started.
Which? said: "Thieves have been using keyless theft - also known as the relay attack - for several years, but manufacturers continue to make new models that can be stolen in this way, meaning there is an ever-larger pool of vehicles for thieves to target."
A Nissan spokesman said: "We are aware of this type of attack and are fully committed and constantly working to protect our customers to tackle the ever changing security requirements.”
Ford and Volkswagen have not yet responded to the Standard's requests for comment this morning.
Additional reporting by Press Association.
