“Relay boxes” can be used to lengthen the signal of a car’s fob and make it appear to be within range. Only the Vauxhall Corsa was deemed safe

Car thefts have risen by almost 50 per cent in four years bearing out a warning that hundreds of the bestselling keyless models are vulnerable to hackers.

Home Office figures showed that 111,999 vehicles were stolen in 2017-18, more than 300 a day on average. This was up from 75,308 in 2013-14, a rise of 49 per cent. Thefts were also revealed to have increased by 15 per cent between 2016-17 and last year.

The consumer group Which? warns today that the vast majority of the bestselling models are susceptible to theft. German researchers tested 237 vehicles and found that all but three were vulnerable to keyless theft or a “relay attack”.

Most new cars are opened and started using a fob rather than with