BMW owners are being warned insurance companies may refuse to pay out if their car is stolen by crooks who reprogram a new set of keys.

Autoblog reported last week on the BBC Watchdog story that revealed thousands of BMWs – built between 2006 and 2011 – were easy targets for crooks who had worked out they could break into the cars, plug a device into the diagnostics system and reprogram a new key in minutes.

Last night the programme highlighted the case of one owner who had been made to feel as if he'd played a part in the theft of his car by insurance company Liverpool Victoria.

The programme reported the owner's story hadn't been believed and that he was asked to prove how his car was stolen.

The insurance firm did eventually settle the claim after a four-month battle but the owner has been left facing higher premiums as a result.

A spokesman for Liverpool Victoria told Autoblog: "The customer made a claim for the theft of his car which we settled in full. Despite these cases highlighted, because of modem technology, it is now very rare for a car to be stolen without the keys and in these cases, a specialist team takes a number of steps to investigate the claim to confirm the circumstances. We regret that in this particular case our enquiries took longer than usual."

But the customer's experience has highlighted a growing concern among BMW owners that their cars won't be covered if they are stolen in a similar way.

As Autoblog reported last week, many owners are taking drastic action and moving the diagnostics port – which the criminals use to crack the keys – into a safer location. There are steps on how this can be done online.

We contacted the Association of British Insurers who told us owners should contact their vehicle's manufacturer if they are aware their car has defects to get it rectified as soon as possible.

A spokesman added: "Insurers will pay out if they believe customers have taken reasonable care of their cars. By that we mean securely locked when unattended."

Concerned BMW owners should call the manufacturer's customer services department on 0800 083 4397 or visit their local dealer. BMW added that models built after 2011 cannot be stolen in the same way.