I believe this is a positive move on behalf of the mobile industry

Jack Wraith

Despite the measure some thieves with access to specialist software could still use the handset by altering its identity number, known as the International Mobile Equipment Identity (IMEI) number.

Industry experts have called for the changing of the IMEI number to be made a criminal offence.

The new system comes into force after Vodafone and BT Cellnet bowed to government pressure to take action against mobile phone thieves.

Virgin, One-to-One and Orange were already able to immobilise handsets using the IMEI number.

'Positive move'

Jack Wraith, a spokesman for the Mobile Phone Industry Crime Action Forum, said: "The five network operators have agreed they will put into place, within the next six weeks, a system whereby they will exchange, between themselves, lists of IMEI numbers of reported stolen handsets.

"When a network sees a mobile connecting to it, it will recognise that mobile as being on any of the lists and bar that number.

"I believe this is a positive move on behalf of the mobile industry."

The move follows a warning to thieves that they will face tougher sentences and a pledge by the Home Office and the Department of Trade and Industry to re-examine industry regulations.

The blocking system being developed by BT Cellnet includes an upgrade which could track the first calls made from a stolen handset on its network.

That could guide police straight to the criminals who stole it, the company said.