Eleven million Nationwide customers may have been put at risk of identity crime after an employee's laptop was stolen.

The computer with customer information on it was stolen during a domestic burglary three months ago.

But details of the serious security lapse are only just emerging.

Nationwide has informed the authorities and will be writing to its 11m customers to give them security advice in the next few weeks.

It is reassuring customers that no PIN numbers, account passwords or memorable information was on the laptop.

But it does not deny that names and account numbers could have been.

If this information was obtained by identity thieves, they could attempt to take out credit cards or open loans in customers' names.

So far there is no indication that has happened according to Nationwide and it said nobody has lost any money.

But if the data is used by criminals it could be some time before any evidence is seen and the fraud attempts may not involve Nationwide.

The names and addresses could be used to attempt fraud elsewhere.