HSBC Holdings PLC, Royal Bank of Scotland Group PLC and six other U.K. lenders won a court bid to halt an antitrust regulator's challenge to fees they charge customers who exceed overdraft limitations.

The Supreme Court, the highest court in Britain, reversed two earlier decisions that ruled overdraft fees are subject to laws regulating unfair terms in consumer contracts. The latest ruling may bar the Office of Fair Trading from challenging the lawfulness of specific terms used by the banks.

Banks earn about one-third of their retail revenue from overdraft charges, according to a market study cited by the OFT. Banks' profit margins are under pressure because they face greater competition for customer accounts to fund lending as wholesale credit markets seized up.

"The banks may not be the most popular institutions in the country at present, but that does not mean that their methods of charging for retail banking services are necessarily unfair when viewed as a whole," Justice Brenda Hale wrote.

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