Eircell has initiated a fraud detection system to combat increasing numbers of criminals who clone chips or steal calls by renting phones with false identity documents. The move has had what the company describes as a dramatic effect on the problem. Esat Digifone says it also now runs a system for curbing fraud.

Specialists within Eircell say that until recently, fraud was not a serious issue in Ireland.

"It was only when the UK mobile operators tightened up the security of their networks that we began to see the first serious fraudsters on this side of the water," said Mr Robbie Lynch, Eircell's network fraud manager.

The company reacted by trying to check call records, check the highest spenders, and co-operate with the Garda. In one case, the company uncovered three men in Dublin selling "cut-price" international calls on cloned analogue - or 088 - mobile phones.

Mr Lynch stressed last night that cloning happens only on analogue, not the more modern GSM or 087 and 086 networks.

But while Eircell was being targeted by organised groups who would scan the airwaves for legitimate customers, then pirate their phones, the company was losing even more in subscription fraud. This saw criminals buying phones with false identity papers, then selling them on to others who would run up huge, unpaid bills. The company also suffered when genuine customers' phones were stolen by people who would then make a series of expensive calls.

Mr Lynch said the company has now adopted a computerised fraud management system made by a British company, Applied IT. The move means it can compile information very quickly, taking data directly from the network switch.

Esat Digifone's chief executive, Mr Barry Maloney, said his company had a similar system in place, used for stopping fraudulent new subscribers and to limit damage if a phone is stolen.