U.K. mobile phone operators Vodafone Group and mmO2, a former division of British Telecommunications PLC (BT), gave way to pressure from the U.K. government on Friday and unveiled plans for combating the country's growing problem of mobile-phone thefts. The package of antitheft measures was quickly endorsed by the U.K. Home Office.

The joint initiative between Vodafone and mmO2's BT Cellnet division focuses on barring SIM (Subscriber Identification Module) cards in all phones reported lost or stolen, and developing a computer system to block calls being made from stolen handsets, the companies said in separate statements.

"I am delighted that mmO2 and Vodafone have agreed to take a big step forward in protecting their customers," Home Office Minister John Denham said in a statement from the Home Office.

The move comes a month after the Home Office published a report estimating that 710,000 mobile phones were stolen in the U.K. last year, more than double the 330,000 mobile phones that were officially reported as stolen or were the target of an unsuccessful theft. Thefts of mobile phones make up one-third of all thefts in the U.K., and an estimated 2 percent of all phone owners have had their mobile phone stolen in the last year, the report said.

The government at the time called on mobile operators to put provisions in place to allow accounts to be cut off when phones have been stolen and IMEI (International Mobile Equipment Identity) numbers compromised. The IMEI number is a unique 15-digit serial number on each phone.

Operators Orange SA, Virgin Mobile Telecoms Ltd. and One2One PLC backed the government's report and said that they were already offering that service. However, Vodafone and BT Cellnet declined to put the technology into place, saying that their older networks did not have the ability to do so.

The joint initiative between Vodafone, mmO2 and retailers seeks to share records of IMEI numbers across all U.K. mobile phone networks. However, the companies stressed that seeking to block IMEI numbers was only a limited solution to cracking down on mobile phone crime.

MmO2 called for a "broader outlook," pointing out that no mobile operator has a foolproof solution to the problem, and warning of the danger of being lulled into a false sense of security through the belief that proprietary mobile-equipment register systems provide a complete answer.

While barring IMEI numbers stops calls from being made on the network, it does not disable the handset from being used, mmO2 and Vodafone said.

The limitation of software solutions is also a problem with another popular mobile phone antitheft technique that has been pioneered by the Amsterdam police and endorsed by the Home Office, the so-called text message bomb. Text message bombs work by bombarding a stolen phone with enough SMS (Short Message Service) text messages to render the phone unusable.

While a unified registration system would prevent phone thieves from simply swapping the SIM card in the phone for use on another network, the problem of duplicate IMEIs on older phones must still be addressed, Vodafone and mmO2 said.

The companies, working with the industry group Mobile Industry Crime Action Forum (MICAF), plan to invite other U.K. mobile operators, mobile-device manufacturers and retailers to collaborate on creating an industry-wide security system that would include a registration scheme to cover not only older handsets but upcoming 3G (third-generation) mobile devices as well, Vodafone and mmO2 said.

One possible hardware solution was promoted last month by U.S.-based custom-logic chip maker Xilinx Inc.: electronic chips that can be reconfigured over a network to shut down a stolen mobile phone.

The company's CoolRunner CPLD (Complex Programmable Logic Device), the CoolRunner-II CPLD, is the type of microchip that is already used in handsets for things like keypad functions, but which Xilinx has engineered so that it can be programmed and reprogrammed over the Internet or wireless networks. If a mobile phone is stolen, the owner could contact their network operator to give the phone's identifier code. The network operator could then send a signal to reconfigure the phone and shut it down, Xilinx said.

Xilinx said it is currently in talks with mobile handset makers.