Barclays has been named the most complained about financial services firm between July and December, with 309,494 complaints over the period and an uphold rate of 66 per cent.
The number of complaints received by Barclays is down by 17 per cent compared to the first half of 2013, when it received 370,733 complaints and had an uphold rate of 62 per cent.
Lloyds Bank received the second highest number of complaints at 256,656, with an uphold rate of 80 per cent, and down by 1 per cent compared to the previous six months.
MBNA received the third highest number of complaints at 213,311, down by 10 per cent on the previous six months.
Bank of Scotland was the fourth most complained about firm with 181,353 complaints, followed by NatWest with 175,731.
In total, there were 2.5 million complaints against financial services firms between July and December 2013, down by 15 per cent compared to the 2.9 million complaints received in the first half of the year.
Payment protection insurance was the most complained about product, accounting for 1.4 million complaints, down by 22 per cent compared to the previous six months.
For decumulation, life and pensions products, Prudential received the highest number of complaints at 6,391, of which 21 per cent were upheld.
Friends Life received the second highest number of life and pensions complaints at 6,219, followed by Phoenix Life at 5,142.
Bank of Scotland received the highest number of mortgage and equity release complaints at 15,075, followed by Santander at 12,257. Nationwide received the third highest mortgage complaints at 5,236.
Adviser network Sesame was the only advice firm to receive enough complaints to be included in the data. The figures relate to firms who have reported over 500 new complaints within a six-month period.
The firm received 1,356 complaints over the period, down by 18 per cent on the 1,646 complaints it received in the previous six months.
FCA chief executive Martin Wheatley says: “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 [fall in complaints] 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.”