The Financial Conduct Authority has revealed that Barclays Bank was the most complained about financial services firm in Britain between January and June of this year.
According to its latest set of data for the first six months of 2014, Barclays Bank received the most amount of complaints with 278,426, although this is a decrease of 10% compared with the second half of last year.
Bank of Scotland came in at a close second with 265,640, after complaints rocketed by 46% since the second half of 2013.
Lloyds Bank came in third with 264,115 complaints, while Natwest and Santander came in fourth and fifth, respectively, with 140,342 and 135,611.
"It's important that firms now get on top of the issues that are driving complaints," said Christopher Woolard, director of policy, risk and research at the FCA.
"Although it's encouraging to see the total number of complaints fall, there is clearly further work to be done to ensure that consumer interests come first."
Complaints about payment protection insurance (PPI) continues to dominate grievance data, according to the FCA.
Customers filed 1,236,899 complaints about PPI, which accounts for 52% of all types of complaints.
PPI was originally designed to provide loan repayment cover, should the customer fall ill, lose their job or have an accident.
However, millions of customers have now submitted complaints stating that that they never wanted or needed the policy in the first place.
Banks have so far set aside £22bn (€28bn, $36bn) to deal with the scandal.
However, the FCA said that the total amount of redress paid fell by 12% from £2.65bn in the second half of 2013 to £2.34bn in the first half of 2014.
"This was largely due to a 17% fall in the number of complaints closed about general insurance and pure protection products (including PPI), which made up 89% of all redress payments in the first half of 2014," said the regulator.