The owner of bargain store TK Maxx has been targeted in what is thought to be the world's biggest ever credit card fraud.
More than 45 million TJX customers have had their details stolen by hackers. The numbers were accessed on the company's systems in Watford, Herts, and Framingham, Massachusetts.
The store denies shoppers at the company's 210 TK Maxx stores in Britain and Ireland are affected.
But a document sent from the company to the US authorities revealed that the hackers appeared to be able to move files between the UK and US computer systems.
President Paul Sweetenham posted a letter to customers saying: "No TK Maxx data was included in the data that we believe was stolen relative to approximately 45.7 million payment cards used in transactions in North America.
"We are fortunate that a number of years ago, the payment card industry in the UK and Ireland began the transition to chip and pin technology for payment cards, which we believe provides an added measure of security for our customers."
The letter added: "We truly regret that this has happened."
Last week police charged six people in Florida with using credit card numbers that investigators believe were stolen from a TJX database to buy about £500,000 worth of electronics and jewellery with Wal-Mart gift vouchers.
Detectives have said they believe the suspects were not the actual hackers but had bought the card numbers from someone else.
The company urged worried customers in the UK to call a hotline on 0800 779015, or 00 44 800 779015 for those in the Republic of Ireland.
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