Payment protection insurance complaints in the past six months have driven grumbles about financial services firms up by 59%.
Data released on September 27 by the Financial Services Authority showed complaints about general insurance and pure protection had risen by 99% to 2,541,430 - 88% of which were about PPI.
Around two-thirds of all PPI complaints have been upheld, and a total of £2.9m in compensation was paid out for insurance products, including PPI, with £3.2bn of redress paid overall in the first six months of this year.
Barclays was the most complained about bank with 442,266 complaints over the six months.
As a group, Lloyds Banking Group, which includes Halifax and Bank of Scotland, witnessed the most complaints.
But if PPI complaints are excluded, Santander and Barclays top the list.
The FSA's data echoes complaints statistics released by the Financial Ombudsman Service on 11 September.
In the FOS data, Barclays again was at the top of the list for complaints, with Lloyds Bank coming in second place.
The British Bankers Association responded to the figures by highlighting that complaints about banks' core product, the current account, had fallen by 13%.
However, the total number of banking complaints had increased by 3%, which the BBA said it would investigate further.
"There will always be instances when things go wrong: when they do, banks are committed to ensuring all complaints are dealt with as fairly, swiftly and effectively as possible," said a spokesman.
On PPI, the spokesman said: "The banks and building societies who sold PPI to customers are working with the FSA, the Financial Ombudsman Service and with consumer organisations to deal with all outstanding complaints from this period as quickly as possible.
"Banks have increased their resources significantly to handle these complaints without delay to ensure that decisions are made as swiftly as possible. At the same time they are writing to customers they believe may have been mis-sold PPI policies in the past advising them of their right to complain."
Consumer lobby group Which? has been at the forefront of helping customers who were mis-sold PPI to reclaim their money, and has called on the banks involved to publish regular updates on how much compensation has been paid out.
Despite more than £10bn being set aside by the banks to pay out PPI claims, Which? claims it won't be enough and is urging the banks to set aside more money.
If PPI payouts continue at the same pace as the first half of this year, Which? predicted Lloyds could run out of mis-selling money by November 2012.
Barclays is predicted to run out by December 2012, RBS within the next six months, and HSBC by August 2013.
It's not clear how many more people are likely to come forward and claim for PPI, although one estimate placed the total payout at £5bn, half the amount set aside by the banks.
There have been suggestions that claims handlers have encouraged the public into applying for claims even when they never took out a PPI policy.
Antonio Horta-Osorio, chief executive of Lloyds Bank, said one in four of its claims related to people who never had a PPI policy with the bank in the first place and that these "spurious claims" are costing the bank money.
A spokeswoman for Lloyds told the BBC in May that even where it was obvious the complaints were bogus, processing these claims still costs time and money.
"If the claim goes on to the ombudsman, that is an additional bill of £850 for the bank," they added.