The Financial Ombudsman Service (FOS) is been urged to consider charging a case fee before the complaint has been resolved and closed, as part of a drive for better efficiency.
A review by the National Audit Office (NAO), published today, said this was one way the organisation could meet the "highly volatile" demand it will continue to face over the coming years.
It pointed out the FOS has seen a 376% growth in number of cases it has had to handle since 2001/2, while it has also experienced a 214% increase in operating costs over the same timescale.
The NAO said the service should "develop a more complete understanding of the factors that are driving its unit costs so that it can begin to address the causes of the increases it has experienced".
Among the key recommendations was that it "evaluate whether its current charging regime is still fit for purpose, and consider charging firms upon case conversion rather than at case closure".
Other recommendations included doing more to quantify the impact of the complexity of cases on unit costs, better understanding the maximum number of cases staff can work on at any one time, and more staff engagement.
Sir Christopher Kelly, chairman of the FOS, said: "As the review concludes, the biggest challenge we face is in dealing with demand that's highly volatile and difficult to predict - while continuing to provide a service that's efficient and value for money, as well as responsive to the needs of our users and stakeholders.
"We're currently consulting on how to gear up to be ready to deal with a further substantial increase in our workload next year - as a result of the rising volumes of payment protection insurance complaints and the impact of the tough economic times on consumers and businesses alike."
The FOS is currently consulting on new charging structures and one of the proposals is to increase the number of free cases for small businesses from three annually to as many as 25.
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