Banks have already set aside 24 billion pounds to compensate customers mis-sold payment protection insurance (PPI) in what has become Britain's costliest consumer finance scandal.
The policies were meant to protect borrowers in the event of sickness or unemployment but were often sold to those who would have been ineligible to claim.
The ombudsman, which deals with cases in which banks and their customers cannot settle a dispute, said it still received about 4,000 complaints a week about mis-sold loan insurance between October and December last year, raising the prospect banks will need to set aside more for compensation.
Last month, Chief Financial Ombudsman Carline Wayman said banks and other financial services firms were likely to be paying out compensation for years to come.
Lloyds Banking Group (>> Lloyds Banking Group PLC) has so far set aside 11.3 billion pounds for compensation, more than any other bank. Barclays (>> Barclays PLC), Royal Bank of Scotland (>> Royal Bank of Scotland Group plc) and HSBC (>> HSBC Holdings plc) have also set aside billions of pounds.
About three out of five cases relating to PPI were settled in favour of the consumer between April and December last year, the ombudsman said. After PPI, bank accounts and mortgages were the next most complained about financial products.
The ombudsman said it received 74,357 new complaints during the fourth quarter, of which 48,516 related to PPI.
That represented a decline on the 57,094 new PPI cases taken on by the ombudsman in the previous quarter and a slowdown from a peak of 12,000 cases a week in late 2012.
(Reporting by Matt Scuffham; Editing by Mark Potter)