An intermittent fault in the Maestro network left thousands of shoppers unable to pay for their purchases over the weekend.
Problems with the chip and Pin systems also hit people trying to withdraw cash – they were told their accounts were empty.
Maestro, is owned by credit card company Mastercard was unable to give information about the failure by 11.30 am on Monday 25 February.
Last September MasterCard launched PayPass, a contactless payments system in London, allowing customers to add contactless payments to their Maestro card for purchases of up to £10 in a range of stores in the City of London and Canary Wharf.
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