Police are repeating warnings to motorists to protect their property after a spate of break ins by thieves targeting a hi-tech car gadget.

Detectives' fears that thefts of satellite-navigation, or satnav, systems from cars could escalate over the festive period have proved to be well-founded.

Detective Inspector Gerry O'Shea, of Bradford North CID, said that in 24 hours between January 3 and 4 alone, there had been sat-nav systems, which at least £300, stolen from vehicles in Wrose, Thackley, Clayton, Chellow Grange and Thornbury.

"Since September there have been more than 300 satnav systems stolen in West Yorkshire and I fear that number may increase if the public do not take simple safety measures to protect their equipment," said Det Insp O'Shea.

"As we expected, thieves in the Bradford area have been taking the opportunity since Christmas to break into cars and steal these saleable items.

"These were the Christmas present of the year and a lot of people bought them."

Det Insp O'Shea said some owners had taken the portable system, which help motorists plot their route as they drive, with them when they left their car but had not removed the sucker holder which attaches the device to the windscreen.

He added: "On some occasions thieves have not been able to take the system, but have still caused damage and disruption and stolen other things to hand, like CD players."

He said drivers needed to follow basic crime prevention rules, including always removing the satnav system, and the sucker holder, and wiping away marks left by the sucker on the windscreen.

They should also not leave other valuables on display, make sure their cars are locked and secure and leave their vehicles in a secure car park - one with a security cameras or patrols.

And Det Insp O'Shea warned people buying stolen systems that they would be caught.

He said: "Some unscrupulous drivers are purchasing these items and they must be aware of their dubious origins."

He said police have been running a crime prevention campaign, handing out leaflets to motorists and putting up posters, urging people to look after their sat-navs.