The figures, released by the City watchdog,
show that 1.3 million grievances were raised against the high street banks in the first six months this year.
Substandard service and poor advice on insurance and mortgages are among the chief complaints of angry customers.
The report also indicates that the banks drag their feet in resolving customers’ complaints,
with less than half dealt with within the recommended time limit of eight weeks.
Marc Gander, of the Consumer Action Group, told the Daily Mail: “We’re used to banks treating their customers shabbily, however these figures are quite extraordinary.
“You have to wonder where these billions of pounds of taxpayers’ money are being spent – it’s certainly not on complaints handling.”