Part-nationalised bank Lloyds received the most complaints among UK financial companies in the second-half of last year, data from the country's Financial Ombudsman body showed Tuesday.
The Ombudsman said the various operations within the Lloyds Banking Group - including the likes of Bank of Scotland and Halifax - got 20,310 complaints from July to December last year.
Barclays got more than 11,500 complaints, MBNA Europe got 9,185 complaints while various operations run by rival part-nationalised lender Royal Bank of Scotland got more than 6,000 complaints.
Most of the complaints were related to the mis-selling of payment protection insurance (PPI) policies, which led Lloyds to take a 3.2 billion pound provision charge last year to cover having to compensate customers who were mis-sold those products.
These policies were typically taken out alongside a personal loan or mortgage to cover repayment if the borrower was unable to pay due to unemployment, sickness or accident.
But they were often mis-sold to the self-employed or unemployed people who would not have been able to claim, and were also mis-sold to consumers who did not realise they were taking out such a policy.
Lloyds said it had managed to reduce the number of complaints it had received in 2011 by 24 percent from a year ago and continued to work hard to improve customer service.
Britains owns 40 percent of Lloyds and 82 percent of RBS after bailing out both banks during the 2008 credit crisis.
(Reporting by Sudip Kar-Gupta; Editing by Myles Neligan)