Bailed-out Lloyds Banking Group topped the bank complaints league so far this year with nearly 290,000 gripes, new figures revealed today.
The state-backed giant's companies generated a total of 288,717 complaints about issues like poor service, bad advice, and charges over the past six months, the Financial Services Authority (FSA) said.
Fellow high street giants Barclays and Santander were the next biggest offenders, with 250,667 and 244,978 complaints respectively. It is the first time the FSA has detailed the findings by firm.
State-controlled outfit Royal Bank of Scotland - whose businesses include RBS and NatWest - drew nearly 140,000 complaints, while HSBC attracted 81,271.
Altogether bank and building society customers made a total of 1.25 million complaints, the FSA said, up 5% on the same period last year.
Among the data published by the FSA was the proportion of complaints dealt with within eight weeks.
Lloyds TSB secured a completion rate of 97% for customers, while Barclays dealt with 91% of cases within the period.
Santander closed only 46% of complaints within eight weeks.
The FSA is proposing changes to its complaints handling rules to help drive up standards.
The proposals include making banks identify a senior manager responsible for complaints handling and creating remedies for common problems.
Officials also want to stop banks sending letters which reject complaints but fail to explain that customers can challenge them and go to the Financial Ombudsman Service.
Sheila Nicoll, the FSA's director of conduct policy, said: "Good complaints handling standards should be the rule not the exception and complaints handling forms a key part of our intensive and intrusive approach to supervise how firms deal with their customers.
"While the FSA's review into complaints handling by banks in April found some good practice, this is far from universal and it is clear that not enough is being done by senior management to prioritise complaints handling. Dealing fairly and effectively with customers who make a complaint provides a valuable opportunity for firms to rebuild and enhance their relationships with their customers.
"We will continue to work closely with firms to help push up standards in this area and to deliver improvements in the way firms treat their customers and we have already referred two firms to enforcement as a result of poor complaints practices.
"The firm specific complaints data published today is also a step in the right direction towards improving transparency for customers."
The British Bankers' Association said the complaint figures should be taken in context with the number of bank accounts,.
It said: "The larger the bank is the more complaints it is statistically likely to receive and with more than 140 million bank accounts in the UK and billions of transactions a year there will inevitably be instances when things go wrong.
"The banking industry welcomes greater transparency but is concerned that the separate publication of complaints data by the Ombudsman and the Regulator could lead to data overload.
"What should be a useful overall summary could become a complex and confusing exercise."