Britian's Financial Ombudsman Service will see a 42pc rise in new claims in the current financial year, driven by an unprecented number of PPI cases, leading to it taking on 1,000 more staff.
The FOS, which deals with cases when banks and their customers cannot agree a settlement, said it had increased the number of expected new cases for the 2011/2012 financial year to 375,000.
That is a 41.8pc rise on new cases made in 2011/2012 which totalled 264,375 and a 21.6pc increase from its initial estimate for the year of 285,000 made in January 2012.
In its latest consultation paper, it said the increase in expected cases was a result of the number of PPI claims, which "dramatically exceeded" their assumptions.
Consumers are currently referring more than 5,000 new PPI cases to the FOS each week, and it expects to receive around 250,000 new cases by the end of the current financial year (2012/2013) against a planning assumption of 165,000 cases.
This has led to the Ombudsman adding around 1,000 more staff to deal with the increased volumes.
"It is disappointing that we are still seeing large numbers of cases that should have been resolved by businesses at earlier stages," the FOS said in its report.
In spite of the boost to staff, it said consumers and businesses would continue to wait "much longer" before cases could be assessed given the high volume of cases being referred, a "challenge seems likely to remain with us for some time indeed, probably for several years".
Aside from PPI, complaints about banking and credit, including mortgages, made up the Ombudsman's largest area of work.
It has currently seen a 15pc rise in the number of these cases compared with 2011/2012, and based on current trends it expects to receive around 77,000 news cases on this subject by the end of 2012/2013.
For non-PPI claims it expects to receive 125,000 claims against the previous forecast of 120,000.
Looking to the next financial year, the Ombudsman said it expected the number of new cases to rise marginally to 385,000.
It said it expects to continue receiving 5,000 cases a week relating to PPI, totalling 250,000 for the year. To deal with the volume it said it was looking to recruit another 1,000 case workers.
For non-PPI claims it expects to receive 135,000 complaints in 2013/2014, up from the revised figure of 125,000 in 2012/2013.
The Ombudsman service is also proposing to increase the fees charged to financial services firms when cases are referred to the ombudsman. The fee will rise by £50 to £550. Additional fees charged on cases relating to payment protection insurance will be kept at £350.