David Beckham's loss of two BMW X5s to car crooks has caused speculation about a new breed of sophisticated thief who travels armed with a laptop rather than a crowbar.

Reports highlighted a new risk to owners of premium models equipped with keyless entry and start-up systems from security software code breakers.

But international vehicle security consultancy SBD believes accounts of the BMW's security system being cracked in a matter of minutes may be wide of the mark.

Its research into vehicle immobiliser technology reveals the protection to be robust enough to require more than a few minutes' tinkering to be disarmed.

David Bell, managing director said: "The level of encryption in a transponder is so high, that even a thief equipped with the appropriate software would need much longer than the time suggested for the taking away of Beckham's BMW.

"The computing power required to break down the protection is way beyond the capacity of a laptop, unless the thieves have previously managed to source confidential security data about the car.

"Of greater concern than computer code cracking is the security provided by motor manufacturers and dealers to prevent bogus or criminal access to replacement keys and immobilisers."

SBD's report revealed that aftersales staff often fail to authenticate documentation and proof of identity and demonstrated how some manufacturers operate inadequate security procedures.