Up to thirty five thousand customers of Santander have received other people’s bank statements, in a major IT blunder.

Santander, which owns Alliance & Leicester and Bradford & Bingley, said recipients had been sent their own transactions and those of others.

Customers who received the statements are able to see other people’s names, account numbers and where they have spent their money.

Santander blamed a “technical error” at its printers, indicating an IT application was to blame. It avoided more error because its system at the printers resets itself every 35,000 statements.

The Information Commissioner immediately released a statement saying he was investigating the incident. Santander apologised, and has notified the Financial Services Authority, but insisted there was no risk of fraud.

"We want to reassure customers that the risk of fraud on their account has not been increased because of this error and that this is a one-off incident," Santander said.