If the Office of Fair Trading (OFT) enforces a cap on unauthorised overdraft charges, banks are likely to respond by introducing a charge for basic banking services, according to Defaqto, the research group.

Banks make an estimated £4.7 billion from unauthorised overdraft charges every year. The OFT is investigating whether to limit the default charges levied on customers who exceed their authorised overdraft limit, after the implementation this year of a £12 cap on credit card default charges.

Average charges on bank and building society accounts have increased by up to 20 per cent in the past three years. Bank of Scotland and Halifax charge the highest fees at £39 for each unpaid direct debit or standing order on an account.

David Black, head of banking at Defaqto, said: “Someone has to pay for banking services and at the moment customers who incur overdraft charges are paying for the free service enjoyed by others — the poor are subsidising the better off. But regulatory changes may result in a move towards charging a compulsory account maintenance fee.”

Some banks charge a monthly fee on accounts that offer additional benefits, such as free annual travel insurance, but the majority of current accounts in the UK are free.

Ed Wells, of Troika, a financial services consultancy, said: “The UK is fairly unusual in that most other countries do levy charges for standard banking services. Banks believe that by changing their charging structures, they will be able to offer more transparent, and also fairer, pricing of their products and services.”

The OFT launched its investigation into overdraft charges last week. It is expected to report initial findings within six months.

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