Current account holders at Santander branches may have received the wrong statement this week after a printing error on 18 December.
The Spanish chain admitted the fault after 35,000 statements were sent to the wrong recipients. The statements had the right details on the first page, followed by someone else's bank account details on the second and third pages.
These pages also included the name and the account number of the person whose bank account it is, which could lead to major security fears for these current account holders.
In an attempt to prevent any identity fraud arising from the error, the bank said it will be asking extra security questions so that people cannot access the accounts of the people whose details they have received.
A Santander spokesperson said, "We are sorry for any inconvenience this has caused and have taken immediate steps to correct this."
"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," they added.
Anyone who wants to change bank as a result of this error should make sure they shop around for the best rates online.
