The number of new complaints received the Financial Ombudsman Service more than doubled to 508,881 in 2012/13.
In its annual results today, the Ombudsman said the number of new cases was up 92 per cent on last year's 264,375.
This is the highest volume of complaints received by the Ombudsman since 2000.
The increase was due mainly to a 140 per cent increase in complaints about payment protection insurance. Some 378,699 complaints were received about PPI, up from 157,716 in 2012. Some 57 per cent of PPI claims were made on behalf of consumers by claims management companies but the Ombudsman said this figure had decreased from 69 per cent in 2012.
The Ombudsman said the increase had 'significantly exceeded' its forecast and it was receiving 2,000 new PPI cases each day.
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This was the largest number of complaints the Ombudsman had ever received for a single product.
Investment-related complaints increased by 33 per cent and banking disputes and insurance complaints (excluding PPI) increased by 20 per cent.
Over half of all complaints were resolved within six months and 43 per cent of non-PPI complaints were resolved within three months.
Ombudsman chief executive Natalie Ceeney said the figures represented a stronger consumer voice.
She said: "We have seen a much stronger consumer voice in the last year- with people becoming more aware of their rights and less willing to put up with poor customer service.
"With complaints doubling, this has been another challenging year for the ombudsman and if consumer dissatisfaction remains at these record levels, the challenges we face are likely to continue for the foreseeable future."

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