Banking giant Santander has sent up to 35,000 people bank statements with the wrong customer's details after a "technical error" at its printers meant that other customers' statements appeared alongside current account holders' transactions..
The bank has apologised, but said there was no added risk of fraud as a result.
"We are sorry for any inconvenience this has caused and have taken immediate steps to correct this," said a spokesman for Santander UK, which formed through its takeover of Abbey, Alliance & Leicester and Bradford & Bingley's retail arm.
"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."
Customers' accounts could not be accessed using the information found on the statement, the Spanish-owned bank added.
The bank has five million current account holders in the UK.