Complaints data published by the FCA has showed 2,479,029 new complaints opened against financial services firms between July and December 2013.
However, the regulator calculated the level of complaints had fallen by 15% compared to the 2,911,154 complaints reported in the previous six months.
Payment protection insurance (PPI) topped the list of the most complained about products during the period with 1,390,756 new cases opened, a 22% decrease on the first half of 2013.
PPI accounted for 56% of all complaints, although this is down from 62% in the first half of 2013.
Redress paid in the second half of 2013 was £2.65bn, up from £2.55bn in the first half of the year. Some 94% of all redress payments were paid for general insurance and pure protection products which include PPI.
General insurance products came second to PPI for the most new complaints, with 321,812, a 3% increase on the previous half-year.
Current accounts, credit cards and the subset of savings including cash ISAs and banking products completed the top five.
In the general insurance and pure protection category, which includes PPI, Barclays Bank topped the complaints charts with 222,946 new cases.
The top five firms for new complaints opened in the second half of 2013, were:
• Barclays Bank - 309,494
• Lloyds Bank - 256,656
• MBNA - 213,311
• Bank of Scotland - 181,353
• National Westminster Bank - 175,731
Martin Wheatley, FCA chief executive, said: "No firm wants to top this particular list and they all should be striving to ensure that customers are being treated fairly and not given cause to complain.
"This is an indication that firms seem to be putting customers at the heart of their business, however, there is clearly more for us all to do to show consumers their interests come first."
