The FOS has released details of complaints over the past six months, showing that it took on almost 150,000 new cases in the second half of 2016.
Complaints about packaged bank accounts have fallen by around half to 9,100, after the FOS worked closely with businesses and claims managers to reduce problems, it said.
General insurance, however, saw a 5% increase in complaints compared to the first half of 2016, reaching almost 18,000.
The FOS received just over 5,000 payday lending complaints, and over 78,000 PPI complaints. PPI accounts for over half of all complaints, it said.
Complaints were received about 234 businesses, and most of those named for the first time are payday lenders or debt collectors.
The FOS found in the consumer's favour in 42% of cases, although this ranges from 6% for Coventry building society to 87% for HFC Bank, it said.
Bank of Scotland was the most complained-about business, with 19,555 complaints. Lloyds and Barclays were in second and third place with 18,411 and 13,379 complaints respectively.
Financial regulations expert Michael Ruck of Pinsent Masons, the law firm behind Out-Law.com said: "While PPI and payday loans may be thought of by many as being old news, the data released by the FOS makes it clear that these issues continue to be at the forefront of complaints made regarding the financial services industry. The risk for the industry is that the regulators consider it is not learning the right lessons and impose ever increasing penalties for failings in these areas."
The FOS is the independent body which deals with complaints by individual consumers against financial services companies which cannot be resolved through that company's own procedures. It is funded by a general levy on the financial services industry, calculated in line with the estimated proportion of complaints generated by each of the different sectors, as well as individual case fees charged to those firms which generate the largest number of complaints.