Lives are being put at risk by thieves stealing expensive equipment from ambulances.

The callous criminals have even been luring ambulance crews to bogus emergencies so they can take the vehicles' satellite navigation systems while the paramedics are looking for a false address on foot.

But ambulance and police chiefs have revealed that the thefts are pointless because the villains can only get away with the screen units - which are useless on their own.

John Darley, operations director for Yorkshire Ambulance Service, said that about 20 of the screens, which can cost up to £1,500 to replace, had been stolen in the past year.

He said: "Thieves have been targeting our ambulances and rapid response vehicles, oblivious to the fact that the equipment is specially designed for use in emergency vehicles and is useless to domestic cars.

"These mindless thefts are leaving the service with vehicles out of operation while repairs are completed and ambulance crews who have to respond to emergencies and find addresses without the assistance of satellite navigation.

"It is beyond belief that most incidents occur when our vehicles are involved in an emergency and those carrying out the crimes clearly have no thought or consideration about the effect this may potentially have on the emergency service delivered to patients in West Yorkshire.

"This is a problem that we shouldn't have to encounter and we ask thieves to consider their actions and think about how these petty crimes are potentially putting people's lives at risk."

Detective Inspector John Minary, West Yorkshire Police's crime reduction officer, said the thefts were particularly serious because hoax callers were luring ambulance crews to false addresses and stealing the sat-nav screens while paramedics were looking for the non-existent location on foot.

Det Insp Minary said: "This is a serious offence as it could ultimately cost the lives of those who make legitimate calls for an ambulance and we want to make it quite clear that crimes of this nature are being taken very seriously."

Police say the main unit of the sat-nav system is impossible to remove by opportunist thieves, and the screens are of no use to them.

Det Insp Minary added: "This type of crime is both serious and ultimately pointless as the items being taken from vehicles are of no use to thieves. They are merely screen units that are of little re-sale value or practical use once they are removed from the main sat-nav unit."

Police are also warning motorists generally to protect their sat-nav systems, which have become a major target for thieves.

Det Insp Minary urged them to remove sat-navs from their vehicles when not driving, and not leave them in their glove compartments.

He said: "Leave no hint to a prospective criminal that you may have hidden something valuable in your car.

"Your glove box should be left empty and open and you should also remove any holders or brackets that are used to attach expensive equipment to your car's interior as this could tell criminals that there is something hidden in your car worth finding."

He advised owners to mark their sat-navs with UV pens and keep a note of the serial number, make and model.

e-mail: steve.wright@bradford.newsquest.co.uk