The Financial Ombudsman Service upheld 82 per cent of investment complaints against Barclays Bank for cases submitted between July and December last year.
The latest data from the FOS shows Lloyds Banking Group topped the complaint list, generating 22,181 new complaints in the second half of 2010.
The FOS received 12,234 complaints about Lloyds TSB Bank, with 8,378 relating to general insurance products such as payment protection insurance.
The FOS resolved 88 per cent of GI cases against Lloyds TSB in favour of the consumer and 73 per cent of investment cases.
Royal Bank of Scotland had 8,644 complaints, with 3,760 through NatWest and 3,286 through RBS. For NatWest, 52 per cent of cases were upheld in favour of the complainant and 60 per cent of RBS cases were upheld.
Barclays had 8,256 complaints across the group and 6,535 related to Barclays Bank. For the bank, 56 per cent of cases were upheld, with 82 per cent of investment cases upheld and 75 per cent of GI cases upheld.
HSBC saw 8,238 complaints and Santander 7,479, with 27 per cent of HSBC cases upheld and 39 per cent of Santander cases upheld.
On average, 53 per cent of complaints were upheld across all financial services businesses included in the FOS data. The figures cover financial businesses that received at least 30 new cases and resolved at least 30 cases in the six-month period. The second-half figure was a rise from 44 per cent in the first six months of the year.
The FOS says complaints relating to these businesses made up around 90 per cent of the total number of cases handled by the ombudsman service.
Towry had the most adviser complaints, with 349 cases. The FOS upheld 84 per cent of complaints against the firm, 83 per cent of which were investment-related.
AWD Chase de Vere had 91 complaints and 58 per cent of closed cases were upheld while Norwich & Peterborough Building Society, which distributed Keydata products, had 73 complaints and 41 per cent were upheld.
Sesame Bankhall Group had a total of 76 complaints and the FOS upheld 60 per cent of closed cases.
Openwork got 41 complaints and 24 per cent were upheld, Positive Solutions had 37 complaints, with 65 per cent upheld, and St James’s Place had 35 complaints and 46 per cent were upheld.
Sesame had 67 per cent of investment cases upheld. Other adviser firms either had no investment complaints or fewer than 30.
Which? chief executive Peter Vicary-Smith says the volume of banking complaints reflect the sales culture “inherent” in high-street banks. He says: “These figures reaffirm the need for a fundamental overhaul to the way many banks pay their staff. When bonus structures reward staff for selling products which may be unsuitable, is it any wonder that we are seeing this level of complaints?”
Evolve Financial Planning director Jason Witcombe says: “As long as banks are making money from pushing their own products, they will continue to do that whether clients really need those products or not. This has got to change.”