Free postcoding for laptops is being offered by Oxford police following a spate of computer thefts in the city.

Businesses across the county are also being urged to tighten up security in the wake of a rise in laptop thefts of almost 20 per cent. Up to 260 computers a month are now stolen across the Thames Valley region, a figure which is being viewed with alarm by the Oxfordshire Chamber of Commerce.

Bill McCardle, the chamber's policy manager, said: "Losing a laptop can be devastating for a business, especially if the files and contact details on it have not been backed up.

"We are urging all local companies with laptops to review security arrangements, to make sure files are regularly backed up and that laptops are not left unattended."

Computers have been stolen from cars as well as businesses themselves, with thieves posing as visitors or cleaners.

Det Sgt Dave Herniman, the head of Oxford police's burglary team, said: "Make sure valuables such as laptops or other expensive items of electrical equipment are hidden from view, particularly if you are away on your holidays.

"We would urge anyone offered a second-hand laptop at a knock-down rate to be suspicious.

Chief Insp Barry Keane, of the Thames Valley Business Crime Centre, said major manufacturers had a responsibility to develop software which would make laptops useless to thieves.

Thames Valley Police has created a website full of advice designed to help firms combat business-related crime. It is at www.businesscrime.co.uk.

Pc John Mulloy of Cowley's crime reduction office can postcode laptops for free. He can be contacted on 01865 335175. Police are asking anyone offered a suspicious second hand laptop computer for sale to contact 01865 266333 or Crimestoppers anonymously for 0800 555 111.