More than two million complaints from disgruntled financial services customers flooded into the ombudsman over the past year.
The Financial Ombudsman Service answered 40,000 queries from the public each week and settled a record 518,778 disputes, which was more than double the amount from last year.
In more than half of cases resolved, the ombudsman found in the consumer's favour - with 58% of those financial services customers receiving compensation.
Some 63% of complaints were to do with the big four banking groups - Lloyds, RBS, HSBC and Barclays.
The vast majority of cases (78%) related to the mis-selling of payment protection insurance (PPI). And the number of PPI complaints was up 6% to 399,939, compared to the previous year.
Other than PPI, most new complaints received were to do with current accounts, mortgages and credit cards.
Complaints about packaged bank accounts tripled over the period, while those about credit cards almost halved.
Tony Boorman, chief ombudsman, said: "It's been an unprecedented 12 months for the ombudsman by anyone's standards. Complaints continued at record levels - and we resolved over half a million cases during the year.
He added: "Each case we see tells a story about the lives and livelihoods of the individuals involved. In our experience, people are simply looking for honest, straightforward answers that show someone has listened and helped make sense of things.
"So whether it's dealing with a complex pension complaint or problems with a mobile banking app, the financial services sector continues to face the challenge of putting the customer at the centre of their business."