Four of the five best-selling car models in the UK are “susceptible to keyless theft”, it is claimed.
Consumer group Which? said Ford Fiesta, Volkswagen Golf, Nissan Qashqai and Ford Focus were at risk.
The other car in the top five – 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.”
But the Society of Motor Manufacturers and Traders said new cars were “more secure than ever”.
Head Mike Hawes told the BBC: “Industry takes vehicle crime extremely seriously and any claims otherwise are categorically untrue.
“Criminals will always look for new ways to steal cars; it’s an ongoing battle and why manufacturers continue to invest billions in ever more sophisticated security features.”