THEY may be the latest "must have" motoring gadgets, but the ease with which satellite navigation systems can be stolen has created a crimewave that threatens to derail a nationwide fall in vehicle break-ins.

Car break-ins have fallen dramatically in recent years after motor manufacturers responded to thefts of car radios by making them harder to steal and sell on.

The reductions have been highlighted in Home Office crime statistics as proof the Government is doing well in the fight against car crime. The most recent national figures revealed a four per cent drop in thefts and break-ins to 176,000 in the three months to September last year.

But the ease with which portable satellite navigation systems can be stolen is threatening to reverse the trend.

Portable units mounted in easy view are an invitation to thieves. The plastic mountings have no security and can be removed from a vehicle in seconds. North-East forces said last night that hundreds had been stolen in the past couple of months.

In County Durham, 103 systems were stolen in six months - 91 of them in Darlington alone and most of the rest in the south of the county.

Middlesbrough has also been affected, with Cleveland Police warning motorists to remove all signs of the devices when they leave their cars unattended.

It is not only an urban menace. In the past ten days, five systems have been stolen from the villages of Neasham and Hurworth, near Darlington.

There have been 38 reported thefts of satellite navigation systems in North Yorkshire this year.

And the problem could be growing - of the 91 thefts in Darlington, 62 were in the past three months.

Jacqui Snowball, of Darlington Neighbourhood Watch, said: "These figures only include actual thefts, there have also been a number of incidents which have been recorded as criminal damage or attempted theft, where no equipment has been stolen but cars have been broken into in search of it."

Drivers are being advised to not only remove the devices from their vehicles, but also the cradles they sit in.

Thieves check rows of cars looking for signs of the systems. If they spot holders or sucker marks, they break into the car and look in the glove compartment.

Tony Lidgate, spokesman for North Yorkshire Police, said: "Drivers need to give their windscreen a wipe so there are no visible marks left. Car break-ins have a terrible impact on people's lives."

Ms Snowball said: "Offences are happening daytime as well as overnight - it can only take a minute to smash a window and grab the unit.

"Offences have occurred on busy highways, outside commercial premises, in residential areas and outside a public house. A number have been taken from vehicles while drivers have been out of their van for just a moment delivering goods."

The theft of satellite navigation systems accounts for eight per cent of car crime nationally, but that figure is expected to grow when the next set of figures is published.

Some equipment has a unique identification number, like mobile phones, which can be registered on the Home Office-approved website, www.immob ilise.com

Ultra-violet marker pens and tamper-resistant tax discs bearing the message "Zero the Opportunity, remove all valuables from view" are also available from local police and Neighbourhood Watch schemes.

Anyone with information about car crime is asked to ring Crimestoppers on 0800 555 111.