Clydesdale Bank has been fined £20.7 million by the Financial Conduct Authority in a record penalty relating to the bank's "serious failings" in handling payment protection insurance (PPI) complaints.
The chief executive of Clydesdale Bank has apologised after it was fined £8.9 million over mortgage failings.
David Thorburn said in a statement:
Clydesdale has agreed to compensate those who were adversely affected, resulting in a total cost to the bank of about £42 million.
The shortfalls in Clydesdale mortgages range from less than £20 to more than £18,000, with an average of £970, the City regulator found.
Clydesdale, which is owned by National Australia Bank, sent letters to customers in 2009 which suggested they had no alternative but to bring their repayments up to date
However, many customers could have rejected demands to repay the shortfalls caused by Clydesdale's calculation errors.
Clydesdale Bank has been fined £8.9 million by the City regulator after it forced 22,000 customers into higher mortgage repayments in order to rectify a previous error by bank staff.
The Financial Conduct Authority (FCA) said Clydesdale had failed to clearly spell out customers' rights following the bank's miscalculation on the repayments on more than 42,500 mortgages.
The earlier mistake meant a total shortfall of £21.2 million in Clydesdale mortgages, with customers who underpaid left with outstanding mortgage balances higher than they should have been.