At least 45.7 million customers of US retailer TJX, which owns UK outlet TKMaxx, have had their bank card details stolen by computer hackers.
US watchdogs were told that the information was taken from TJX's computer systems in Watford, Hertfordshire, and Massachusetts, but the firm has revealed it did not know how many of the customers affected were from the UK and Ireland.
In what is thought to be the largest credit card scam in the world, hackers first accessed TJX's systems in July 2005. However the group asserts that no customer data was stolen after December 18th last year.
"We suspect that customer data for payment card transactions at TK Maxx stores in the UK and Ireland has been stolen," said the company.
It added: "We suspect that these files contained payment card transaction data, some or all of which could have been unencrypted and unmasked."
The company is urging its customers in the UK and Ireland to carefully check their bank accounts to detect any fraudulent activities and has set up a helpline for any concerned customers.
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