Approx. 700,000 mobile phones were stolen in 2001

Around 440,330 phones have been blocked from all mobile networks as part of an industry-wide initiative which began last November.

But members of the Mobile Industry Crime Action Forum (MICAF), which is behind the scheme, admit reprogramming stolen phones in still "relatively easy" and its scale is hard to measure.

Home Secretary David Blunkett made the announcement during the launch of a �1.5m advertising campaign designed to show mobile phone thieves that stolen handsets are virtually worthless.

Street crime

Mr Blunkett said: "We are doing everyone a favour by getting the message across that as soon as phone is taken people can get it immediately cut off and we can stop it being a worthwhile thing to do.

"This initiative will make a tremendous difference."

Metropolitan Chief Constable Sir John Stevens said he believed the scheme was extremely important.

He said mobile phone theft made up 50% of street crime in London and 30% of street crime nationwide.

To block a stolen handset Call 08701 123123

Mr Stevens said arrests of those attempting to reprogramme stolen phones had already taken place, including three in west London on Tuesday morning.

He said: "Anyone who thinks they can get away with cloning phones is in for a shock."

Reprogramming can be achieved with little more than basic technical knowledge and access to a computer.

Jack Wraith, from MICAF, admitted: "It is relatively easy to reprogramme a phone and that is why we needed the government legislation in place to assist us.

"This hands out tough penalties to anyone found reprogramming.

"Without this legislation we would have been chasing ghosts."

Posters

Ian Fraser, of mobile phone company Orange, said: "Reprogramming figures are difficult to gauge but the database will provide us with an indication of the level of activity. It is a initiative we support fully."

"Immobilise" billboard posters will appear across the country and are the fruits of a partnership between MICAF, the Home Office and the police.

The measures allow stolen handsets and their SIM cards - the phone's electronic database - to be barred on all networks, making them useless unless illegally re-programmed.

Protecting your phone Get "IMEI" identity number of your phone by dialling *#06# If phone is stolen, contact network and give them your IMEI All calls will then be immediately barred and the number passed onto a shared database

Home Office research published in January last year showed that mobile phones were taken in 28% of robberies, with an estimated 700,000 stolen in 2001.

The Mobile Telephones (Re-programming) Act came into force last October, introducing penalties of up to five years in jail for people caught reprogramming IMEI numbers.

Third generation (3G) mobile phones, launched on Monday and due to hit the shops by April, will be part of the database but may also have additional security features.

One new idea for 3G phones is a "kill" signal sent over the airwaves to stolen handsets by network operators.