Tokyo online fraud detection: Privacy fears as banks track mobile phones: Barclays aims to tackle fraud by introducing system that will check if someone is in the same country as their card

Banks will track customers' movements via their mobile phones in a bid to tackle fraud. Barclays is introducing a system which allows it to check whether someone is in the same country as their debit or credit card so they know whether the payment is fraudulent or not. For example, if a suspicious transaction was made in the America, but data showed the customer's phone it was in the UK, the bank would realise something was amiss. However, if the customer's phone was also in America, it would perhaps prevent the bank from unnecessarily blocking the card.

Money Mail has seen details of the plans in new terms and conditions sent to Barclays' customers. Barclays says the system will help to tackle the boom in UK fraud, which now costs up to £193billion a year. It says customers will be able to opt out of the scheme.

But critics say that tracking customers through their mobile phone data raises privacy concerns. Renate Samson, of campaign group Big Brother Watch, said: 'Customers should be fully informed and asked if they want this service, rather than it being buried in the terms and conditions.

'The other issue that this raises is around data protection and whether your information is being shared with third parties. You should be fully informed as to who is getting your data and why.'

It is thought Barclays is working with mobile phone networks on the plans. A spokeswoman for Barclays said it would not be compulsory and customers would have a choice over whether or not they wanted to be included.  She told Money Mail: 'This service will only be used for fraud prevention purposes. 'Only when an out of character transaction has been detected by our fraud detection systems will we confirm that the customer is in the region where the transaction was made.

'When the service goes live it will operate at a country-level only and help us to detect if a payment made abroad is genuine or should be blocked.'

She insisted that Barclays had 'no higher priority than the protection of our customers' funds and data'.