Mark Simpson BBC News, Manchester

Drivers are advised to remove their sat-navs when they leave the car

That is the message from police forces around the country as thefts of 'sat nav' devices rise at an alarming rate.

For many of us, it was a must-have Christmas present. Sadly, it is rapidly becoming a must-steal item for car crooks.

No official UK-wide statistics exist, but it is estimated that a quarter of a million sat navs were stolen last year.

Believe it or not, some were even taken from ambulances.

Hi-tech thieves

And it is not just a big city problem, it is happening across the UK.

Look at your local newspaper and the chances are that a theft has been reported in your area.

Trawl through the internet and you see recent stories in the Milton Keynes Citizen, the Derby Evening Telegraph, the Belfast Telegraph, the Portsmouth News, the Newcastle Journal, Peterborough Evening Telegraph and even the Rye & Battle Observer.

Thieves at the moment are using the latest technology, which can track a sat nav system even when it isn't on display in a vehicle Detective Sergeant John Agor

In west Yorkshire there are, on average, more than 300 sat navs stolen each month and car crooks are becoming increasingly cunning.

Detective Sergeant John Agar from the force's vehicle crime team explains: "Thieves at the moment are using the latest technology, which can track a sat nav system even when it isn't on display in a vehicle.

"So, for example, if your car is parked up and the sat nav is locked in the glove compartment, thieves can still tell it is there and will break into your car for it."

Drivers are advised to adopt a three-point safety plan in order to ensure their sat nav is not the next one to be stolen:

• take it out of your car when you leave

• remove the suction pad from the windscreen

• hide the suction pad away and wipe your windscreen down.

Thieves will often look for marks where the sat nav has been and break into the car to try to find it. Even if you have taken your device away, you will still be faced with a broken car window.

Police are also advising drivers to security mark their systems with their postcode, and also the registration number of their car, so if it does get stolen, it makes it easier for police to identify, and return to the owner.

According to a car crime survey last year on behalf of Autoglass, sales of sat navs are heading towards six million. It is a lucrative business with devices costing between �150 and �1,000.

Ambulances targetted

On the black market, they are going for less than �100 but the thieves regard it as easy money, given how quickly they can steal them.

Sat-navs are sold for a fraction of their value on the black market

The most sickening aspect of this new crime wave is the targeting of ambulances. The latest was on Wednesday in Tyneside. The vehicle was forced off the road, while a replacement system was fitted.

To try to keep up with the thieves, the police have organised a number of 'sting' operations in which dummy devices are left in cars, and when the crooks try to steal them, they are caught red-handed.

This has worked well in Manchester in a joint venture by the police and NCP car parks.

However, the authorities say the best person to stop the thief is the driver. Everyone should ensure that sat navs are not left in cars.