Bank charges was the most common complaint subject last year
More complaints have been made to the financial ombudsman about controversial loan insurance than any other subject this year.
At least 25,000 consumer complaints have been made to the service about mis-selling of payment protection insurance (PPI).
A number of companies have been fined by the City watchdog for selling PPI to people who do not want or need it.
Credit card charges were the source of about 10,000 complaints this year.
Together these two subjects have prompted more complaints to the ombudsman than the issue of bank overdraft charges last year.
PPI covers repayments on loans or credit cards if the borrower is unable to pay because of loss of earnings caused by accident, illness, unemployment or death.
It has been the subject of a number of inquiries.
The latest by the Competition Commission found that in 2006, of the £3.5bn of the insurance sold by 12 largest sellers, £1.4bn was "excess profit" for the banks and institutions that sold the policies.
Nineteen firms have been penalised by the Financial Services Authority for mis-selling PPI, and this has led to a string of complaints by individual consumers to the Financial Ombudsman Service which can order refunds or compensation.
Chief Ombudsman Walter Merricks said that single issue consumer campaigns, driven by the power of the internet, were becoming regular feature of the service's work, rather than dealing with individual's unique financial problems.
"The ombudsman's office was regarded as a kind of craftsman's workshop, not a factory for mass-production," he told Ombudsman News.
"So some eyebrows may be raised at the idea of the ombudsman service now handling a workload involving thousands of similar complaints."
He said that, in the ideal world, financial businesses would treat their customers fairly and put things right if they went wrong.
Collective solutions would be better for issues of widespread consumer detriment, but he accepted that mass surges of single-issue complaints were likely to continue.
"The actions we necessarily have to take, in order to address the complaints, may result in our being accused of acting as a surrogate regulator, but that may be inescapable," he said.