The campaign against high bank charges has been given a boost by research that disclosed that there was more than £2 billion in charges that could be reclaimed.

Thousands of people have already forced their banks to hand back hundreds of pounds charged in overdraft fees. Research from Uswitch, the finance website, suggests that about 19 million people have been hit by bank charges totalling £4 billion, and more than half have still not claimed back money they are due.

About two million people have downloaded pro-forma letters from internet sites, helping them to claim back the charges. Nick White, head of financial services at -USwitch, said that the revolt against bank fees is believed to be costing the banks at least £50 million, although this could be much higher if more people were aware of how to apply to have the charges -refunded. "The majority of banks are bending over backwards to -refund bank charges to those consumers that fight back," he said.

High street banks are -refunding most contested charges because they do not wish to risk a damaging test case in court that could set a legal precedent.

Campaigners argue that the charges of up to £39 levied when customers go overdrawn are unlawful but the banks have not allowed a single case to come to court.

The penalties imposed for unauthorised overdrafts are supposed to cover administration costs. However, campaigners claim the real cost is less than £5.

A pending report by the -Office of Fair Trading is likely to agree that charges are -excessive. It is expected to name a fair level of fees -between £12 and £20.

However, some experts have warned that the introduction of a cap on bank fees could lead to all customers being charged for using their current accounts because the fees currently made large profits for the banks. City bank Credit Suisse says the banking sector could lose £500 million a year if regulators declared fees unlawful.

"The UK is one of the only places in the world that doesn't charge for current accounts. Customers have enjoyed free banking on current accounts for the past 23 years but the current backlash against charges for items such as overdrafts and bounced cheques, as well as ongoing investigations into lucrative financial products such as Payment Protection Insurance (PPI) on loans and credit cards, will serve as a catalyst for the fast introduction of monthly fees," said Mr White, at Uswitch.

The website survey suggested that more than 80 per cent of people would consider switching banks if they were charged for operating a current account.

This research was carried on behalf of Uswitch.com by YouGov among 4,540 British adults.

-- Telegraph