According to press reports the back-up computer tape was being held by data storage firm Iron Mountain. The firm told GE Money that the tape was missing from its warehouse in October.

The tape is thought to contain credit card information for customers of around 230 retailers, including JC Penney. Reports says the tape also includes the social security details of around 150,000 people.

GE Money is reportedly writing to those affected by the data loss and says it will pay for 12 months of credit monitoring for customers whose social security numbers were lost.

The disclosure comes a year after US retailer TJX reported a security breach that resulted in the theft of millions of credit card numbers.

Hackers placed unauthorised software on TJX's computer network and stole at least 100 files containing data on millions of accounts. Debit and credit card data exposed in the breach is thought to have been used to make fraudulent purchases in Florida, Georgia and Louisiana in the US, as well as in Hong Kong and Sweden.

In a separate incident the UK's Ministry of Defence (MoD) has reported that a laptop containing the personal information of 600,000 people has been stolen from a Royal Navy officer.

The MoD says it is writing to around 3500 people whose bank account details were on the laptop. Payments association Apacs is helping to inform banks so that accounts can be monitored.

Other information on the computer includes national insurance numbers and passport details.

The MoD says the information held is not the same for every individual. In some cases the record is no more than a name. But for other "extensive personal data" may be held, including passport details, National Insurance numbers, drivers' licence details, family details, doctors' addresses and National Health Service numbers.