Thieves are putting lives at risk by stealing vital equipment from ambulances.

Around ten satellite navigation systems have been stolen from ambulances and response cars in Sussex over the past year.

Most of the thefts have occurred when paramedics left the ambulances to attend to casualties.

There have also been cases when emergency cars have been vandalised and bags taken from ambulances left open while crews collect emergency patients.

The incidents slow down the response of ambulance drivers being sent to emergencies and means patients could be left waiting longer than normal for life-saving treatment.

Ambulance officer Simon Morton said he was horrified when a sat-nav system was stolen from his emergency car six months ago. He said: "My car was clearly marked and they knew who they were stealing from. I was really upset.

"Our vehicles are becoming more targeted for sat-navs as people are more aware that they are fitted with this sort of equipment.

"It totally impacts on our ability to respond to the situation immediately as we have to revert to maps and often stop at the side of the road. There will be occasions when people's lives are put at risk by such thefts, depending on the severity of the patients condition. The longer you take to respond and get to a patient affects how likely they are to survive."

The best sat navs, which retail at up to £300, can be sold by thieves for £50 to £100.

But the South East Coast Ambulance Service NHS Trust (SECAMS) says the thefts are pointless because the systems used in all ambulances and response cars cannot be used in normal cars.

They are part of an on-board computer system unique to the vehicles, part of an integrated system. Crews sent an emergency call are automatically and electronically sent directions.

Janine Bell, spokeswoman for SECAMS, said: "Obviously not having sat-nav in a vehicle slows down our response to a patient and damage can be done to the vehicle when they are ripped out.

"An ambulance or response car can still operate without them but they are now considered an integral part of our equipment.

"Sat-navs in ambulances are not the same as commercial sat-navs and of little or no use to anyone else."

Thefts have happened in Worthing, Crawley and Brighton, some when the cars were parked and locked outside a paramedic's home while others were during an emergency situation.

A year ago, a crew were in a home in Handcross helping a patient for just 15 minutes and found their navigation system gone.

In October, vandals smashed the windscreen of a paramedic's car with a concrete block in Furnace Green, Crawley, while he was helping an elderly woman who needed emergency treatment for a kidney problem.

The car was off the road for 12 hours, putting extra pressure on the service's resources.

The most recent theft of a sat-nav happened when thieves ripped one of SECAMS' Terafix sat-nav devices from an ambulance while it was parked on the forecourt of Brighton General Hospital The ambulance had to be taken out of service.

Ambulance services around the country have suffered sat-nav thefts including East Midlands Ambulance Service which revealed it had 34 of the devices stolen from ambulances in the past six months.

The thefts cost the ambulance service around £300 to replace each system, meaning SECAMS has been hit with a repair and replacement bill of more than £3,000.

The vehicle is sometimes off the road for several days while repairs are carried out.

Many of the devices are taken in the belief they can be sold.

Sussex Police has issued repeated warnings to motorists during the past year over the theft of sat-nav systems and said paramedic crews should be just as aware of security.

The devices sold in most electrical retailers have a high black market value and can be sold relatively quickly and are difficult to trace.

A Sussex Police spokesman said: "Every motorist, including paramedics, should be aware of security. Theft of sat-nav devices has become a big problem because thieves believe they can be sold."