The gangs employ hi-tech copying equipment and tiny CCTV pinhole cameras to steal both the card details and the Pin numbers keyed in by unsuspecting victims when they use ??hole-in-the-wall?? machines.

Detectives have dubbed the gangs ??the Romanian ring?? because nearly all of those caught have been from eastern Europe. They are believed to have stolen ??5m in the past few months.

The gangs?? leaders have become so sophisticated in their methods that police now believe they are ??franchising?? the equipment to other criminals for ??10,000 a time.

Banks and credit companies are so worried about the gangs?? operations that they are launching a ??10m advertising campaign tomorrow to introduce a new system in which cards are protected against cloning by microchips that will eventually replace the magnetic strips.

Last year fraud committed on British plastic cards fell for the first time in eight years, largely as a result of a clampdown on theft abroad using stolen credit cards. The figure dropped from ??424.6m in 2002 to ??402.4m in 2003. But the banks saw losses from cloning of cards by the Romanian ring and other crooks using more traditional methods leap from ??29m to ??39m.

The gangs usually prey on cash withdrawal machines in places that are deserted overnight. Supermarkets and petrol stations that close in the evening are common targets. They attach a computerised ??reader?? over the slot where cards are inserted. A metal strip with two pinhole cameras is glued out of sight in the recess above where the customer enters the Pin number, or attached to a phoney leaflet holder added to the machine.

The gang hides in a van nearby. When a card is inserted by a victim, the gang??s device reads its magnetic strip and feeds the information back by a radio signal to a laptop computer. A few seconds later the crooks use their CCTV monitor to spy on the customer as he or she enters a Pin number. The criminals can then create a new plastic card complete with magnetic strip and use the Pin number to empty the account.

Rosemary Weaver, 37, a mortgage company manager, fell victim while using her Link card at an Abbey cash withdrawal machine outside a Sainsbury??s store in Bracknell, Berkshire. She said: ??I have always made a point of not using a cash machine if somebody is standing behind me.

??The first I knew that my card had been cloned was when a machine declined to pay me any more cash because it said I had had my maximum limit for that day. The gang had taken ??900 in three separate withdrawals from my account. My bank replaced all the money but I am now wary of all hole-in-the-wall cash machines.??

A 30-strong team of police officers has been set up in the City of London to combat bank and credit card fraud.

Detective Chief Inspector Steve Eastwood, head of the Dedicated Cheque and Plastic Crime Unit (DCPCU), said: ??This is a real growth area. There is a caucus of knowledge that resides within a core of people and they have splintered off into various groups in all areas of the country.??

Jemma Smith, communications manager at the Association for Payment Clearing Services (Apacs), said: ??It is a new twist on the more traditional version of cloning or skimming that takes place in a bar or restaurant where you hand over your card and a corrupt employee swipes the details.

??The gang has adapted the technology to get the double whammy of not only your card but your Pin number as well. The victim does not know what has happened until they get a call from their bank or receive a statement.??

Previously criminals have used ??shoulder surfing??, in which they spy on someone as they enter their Pin number and then steal their card, or a device nicknamed ??the Lebanese loop?? which is placed over a cash machine and appears to swallow the card.

The commercials launched tomorrow will be introduced by ITV announcers as if they are public service broadcasts and will introduce a new ??chip and Pin?? card. It is being billed as the biggest change in the way we pay since decimalisation.

Ten million of the cards have already been produced. They use a computer chip to identify the card. Customers using shops with new computerised terminals will be asked to enter a Pin number on a key pad in shops instead of writing their signature. Banks claim that this will be the norm by next year.

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