The figure, published yesterday by the National Association of Bank Consumers, came on the eve of the traditional post-Christmas spending spree.
The association, which is campaigning to convince banks to introduce photo identification credit and debit cards, yesterday advised consumers to retain all receipts and check bills carefully against monthly statements.
Stuart Cliffe, its chairman, said: "If you find an error on your statement weeks or months after the event, it can be much too late to do anything about it, and your money may be gone forever."
The association yesterday published tips to ensure against fraud and over-charging. Above all, consumers are advised to keep their cards with them at all times, but never in the same place as the Pin number. Emergency telephone numbers and a record of all credit and debit card numbers should be kept in a safe place at home.
All receipts should be retained and checked against bank statements each month. If any discrepancies are found, consumers should immediately contact their bank, both by telephone and by a letter sent the same day. Finally, cards should never be lent to anyone, not even to family members.
"You might expect the January sales will be the next drain on your hard- earned cash," Mr Cliffe said. "But with so many credit card transactions at this time of year, thieves and credit card criminals could also be making merry with your money."