The Financial Ombudsman Service received 159,197 new complaints about financial services companies between April and June - up 179% year-on-year.
The vast majority (132,152 or 83%) were to do with payment protection insurance (PPI), with the FOS receiving around 2,000 new PPI complaints each day.
The FOS found in the consumers' favour 78% of the time in PPI cases.
In June, Lloyds was forced to admit shortcomings in its PPI complaints handling procedures after an undercover Times reporter was told to ignore possible fraud by Lloyds sales staff and that most complainants would give up if their claim was rejected the first time.
Across all complaints, the FOS agreed with complainants in around 70% of claims.
The next most complained about product was current accounts, with 3,873 complaints received during the quarter, of which less than a third (31%) were resolved in the consumer's favour.
The FOS also received 2,941 complaints about mortgages during the quarter, of which just 27% were resolved in the complainant's favour.
The number of complaints about mobile phone insurance during the three months were modest at 114 but the FOS sided with the majority (72%) of consumers.
The Ombudsman also reported seeing more claims regarding motor insurance and the way in which 'wear and tear' is dealt with.
"We continue to see problems arising from disagreements about the cause of the damage to a vehicle - particularly in those cases that involve accidents," said a FOS spokesperson. "We often see consumers and insurers disagreeing about whether all the damage had been caused by the accident - in which case it is the usually the insurer's responsibility to sort it out - or whether some of the damage had been caused by 'wear and tear'."
In one case, a lady had complained that her car had been damaged while being repaired after an accident but her insurer insisted there were pre-existing problems so refused to pay for the further work to correct the problem.
However, she was able to prove the insurer wrong by paying for a local mechanic to fix the problem. When she reported her complaint to the FOS, it ordered her insurer to compensate her for the work, and pay her £150 for her time and the inconvenience.