According to press reports, the bank recently migrated its core technology platform from Experian and onto its in-house Discovery system, but a problem with the switch-over meant statements were sent out to thousands of customers with extra interest incorrectly added on to credit card accounts.

Morgan Stanley has admitted to reporters that it was not until angry customers called up about the charges that it realised there was something wrong.

A number of customers receiving their August statements will see the error, although online statements and September statement will have the correct figure.

A spokeswoman said the bank has resolved the software issue and will ensure that affected customers are reimbursed immediately.