Lloyds Banking Group topped the list for complaints to a consumer watchdog in the first half of the year with payment protection insurance drawing over a quarter of all cases in the finance sector.
The part-nationalised lender and Britain's biggest retail bank was well clear of Barclays and Royal Bank of Scotland.
The financial ombudsman said on Tuesday it dealt with 15,233 complaints from customers at Lloyds, which controls about one third of Britain's mortgage market, against 9,056 at Barclays and 5,883 at RBS.
Insurance to cover debt repayments attracted 18,671 complaints, or 27 percent of the total.
The ombudsman service resolved 81 percent of complaints about Lloyds TSB, Lloyds' main retail banking business, in favour of the customer, against an average of 61 percent for all banking-related complaints.
(Reporting by Myles Neligan; Editing by David Cowell)