Banks in Britain make £2.5 billion in unauthorised overdraft charges every year, the Office of Fair Trading (OFT) is expected to reveal.

The High Court has been investigating the fees and the OFT will produce a report later this month before a ruling is made on whether they are fair.

Eight banks are involved, with findings predicted to show that they made the money on charges for the average daily unauthorised overdraft balance of £600 million in 2006.

Some customers have been refunded for the fees - which could be up to £35 per transaction - though repayments are on hold until the conclusion of proceedings, which began in July last year.

Last month a study by Fairinvestment.co.uk found that over 50 per cent of people in the UK have paid bank fees, with 16 per cent claiming they are charged "constantly" and cannot afford repayments.

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