UK adults have been warned about the impact hidden fees can have on their retirement savings in a new report which shows that charges can halve the value of their pension.

The study from think-tank RSA has shown that around 90 per cent of the country's biggest pension fund managers are not warning their clients about the fees, taxes and commissions which can wipe out up to £100,000 of a middle class worker's pension.

In select cases, a two per cent annual charge levied over the lifetime of a pension can halve the value of a pension.

In order to create more transparent fees, the RSA has called for the introduction of bank account-style statements to explain to employees how fees were likely to reduce their future pension income. 

"For markets to work effectively, consumers need to know what they are buying," the report's co-author David Pitt Watson said.

"It is extraordinary that, after so many years, such a system is not in place in this country."