Financial services firms saw a 2.6% drop off in new complaints between January and June compared with the previous six months, figures from the regulator show.
Some 2.05 million complaints were made to financial firms during the first half of this year, with 57% of complaints upheld in customers' favour, increasing from an uphold rate of 54% between July and December 2015. The total redress paid to consumers in the first half of 2016 was £1.96 billion.
More than half (59%) of new complaints related to advising, selling or arranging a particular product, while 27% of complaints related to admin or customer service.
Within the latest figures, payment protection insurance (PPI) remains the most complained-about product, accounting for 45% of complaints opened between January and June.
Some 927,631 new PPI complaints were received, marking a 0.5% fall compared with July to December 2015.
The uphold rate for general insurance and pure protection products, including PPI, was the highest across all product groups, at nearly 64%.
There was also a sharp reduction in complaints about current accounts - which were the second most complained-about product, behind PPI.
Some 407,954 complaints about current accounts were recorded, marking a fall of 10% or more than 46,000 complaints, compared with the previous six months.
The number of current account complaints recorded in the first half of 2016 was 75% lower than a peak at the end of 2009, but still 42% higher than a low point seen in 2013.
Meanwhile, complaints about savings, i ncluding cash Isas and other banking issues increased by 7% compared with the previous six months, with 73,322 new complaints recorded in the first half of 2016. This figure is still 53% lower than a peak seen at the start of 2010.
Christopher Woolard, director of strategy and competition at the FCA, described the overall reduction in complaints as "encouraging".
He said: "Firms still need to continue to ensure they are doing all they can to reduce consumer dissatisfaction, but the figures show firms are taking our feedback seriously".
Barclays was named by the FCA as the most complained-about firm, receiving 287,463 complaints in the first half of 2016, up by 3% on the previous six months. Barclays has seen a rise in complaints about PPI following pro-active mailing to customers, while its banking complaints have fallen year-on-year.
Barclays pointed to various initiatives it has undertaken to improve customer service, including the introduction of voice security technology to make its telephone banking service easier to use and more secure.
Matt Hammerstein, head of client and customer experience at Barclays, said: " We want everyone to have a brilliant customer experience with Barclays and will not stop until we achieve this. We are listening to feedback so we can fix the things that aren't working and exceed what our customers expect from their bank."
Financial firms have a duty to provide the FCA with information every six months about the complaints they have received.
Here are the most complained-about financial products between January and June 2016, with the number of complaints received by firms and the percentage change compared with the previous six months, according to the FCA's figures:
:: PPI, 927,631, 0.5% decrease
:: Current accounts, 407,954, 10% decrease
:: Other general insurance, 300,903, 1% increase
:: Credit cards, 129,770, 1% decrease
:: Savings including cash Isas and other banking, 73,322, 7% increase
Here are the five most complained-about financial firms, according to the FCA, with the number of complaints they received between January and June 2016 and the percentage change compared with the previous six months (figures exclude complaints relating to consumer credit):
1. Barclays Bank, 287,463, 3% increase
2. Lloyds Bank, 213,163, 7% decrease
3. Bank of Scotland, 173,646, 5% decrease
4. HSBC, 124,891, 3% increase
5. NatWest, 121,197, 10% decrease