Marketing firm Epsilon have promised a full investigation into the data breach Related Stories
Marks and Spencer customers have been warned to expect an increase in spam e-mail after hackers stole their details.
The company has contacted users of its online service to warn them about the data breach, which was part of a wider attack on marketing firm Epsilon.
A number of American companies also had their mailing lists compromised, including the hotel chains Marriott and Hilton as well as several banks.
Marks and Spencer said that customers financial details were safe.
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