Barclays was the most complained about firm during the second half of 2011, according to the Financial Ombudsman Service.

The FOS received 11,577 new cases about Barclays from 1 July to 31 December 2011.

This included 3,474 complaints about banking and credit, 458 about mortgages and 361 about investments.

The main bulk of complaints were regarding payment protection insurance, the FOS received over 7,000 complaints regarding Barclays mis-selling PPI.

Some 99 per cent of PPI complaints were resolved in the favour of the consumer.

Barclays was one of the largest sellers of PPI and has put aside over £1bn for consumer redress.

Regarding complaints overall, 84 per cent of complaints were resolved in the favour of the consumer, the average for all businesses was 72 per cent.

Barclays also received 16,864 complaints during the first half of the year, bringing the total for 2011 to 28,388.

Natalie Ceeney, chief executive and chief ombudsman, said: “The proportion of complaints that we have upheld in favour of the consumer, ranging from six per cent to 100 per cent, clearly highlights the difference in PPI complaints handling across major businesses over this period.

“It also reflects the efforts made by some businesses to resolve quickly the hundreds of thousands of PPI complaints that had built up during the banks’ unsuccessful PPI legal challenge.”