Known by security services worldwide as the “terrorists’ friend”, the phones have been used by militants to contact each other without being eavesdropped and to trigger bomb attacks, as in the strike in Madrid last year.

Mobiles are believed to have been used by the 7/7 bombers as timers in their rucksack bombs which killed 56 people.

The pay-as-you-go mobile can be bought over the counter with no trace of the owner. Counter-terror police admit that tracing mobile telephone calls by terror cells has been a vital tool in thwarting attacks in Britain.

One security source said: “Anything that makes it easier to track who owns phones is obviously an advantage though the practical difficulties of regulating the use of mobiles is obviously huge.”

Lim Keng Yaik, the Malaysian Communications Minister, announced that from the end of the year people using a pre-paid service will have to register their details with phone companies. Customers will be have to show identity cards or passports when they buy a new sim card. Existing users will have to register when they buy more credit.

Police are concerned that new mobile technologies, such as phones that run on the 3G network, are making it more difficult for security forces to listen in on suspected terror cells. Text and voice carried over 3G phone networks are more spread out and thus more difficult to intercept.

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