Thefts of sat-nav kits in the UK are higher than ever before, as the must-have car accessory is easy prey for thieves.

In some areas, levels of theft are five to 10 times higher than just a few years ago, sat-nav thefts are to blame. "Huge" numbers of sat-nav units are being stolen on a weekly basis, police forces say.

Too many drivers leave their sat-nav device on view or switched on when they leave their car, or fail to clean off the ring that the cradle normally leaves on the windscreen, according to police chiefs.

London is leading the sat-nav thefts league - as many as 36 devices are stolen each day in the capital, the Metropolitan Police said, with nearly 13,000 stolen last year alone.

Despite repeated warnings, the snatch rate continues to soar in the rest of the country too. In Staffordshire, thefts rose to a record high of 600 in the first eight months of 2005 from just 18 in 2004. The authorities fitted tracking devices to portable devices to help catch thieves at the time.

"If you have stuff on view, it will go," said Staffordshire crime reduction officer Jane Jepson.

South Yorkshire crime reduction boss Andy Foster added: "It's like leaving £200 on the dash." He also warned that thieves are using Bluetooth technology to track units that have been left on but hidden in cars.