Last month, the High Court ruled in favour of the Office of Fair Trading (OFT), allowing the watchdog to press ahead with a probe into whether banks can legally charge customers penalty fees as high as £30 for slipping into the red without prior agreement or for bouncing a cheque. This paved the way for current- account holders to reclaim billions of pounds in fees.

However, Mr Justice Andrew Smith last week allowed the banks to appeal against his first ruling that the OFT had jurisdiction over charges. If that appeal is successful, then any separate decision on fairness would be made redundant.

Peter Vicary-Smith of consumer group Which?, said the move was a “kick in the teeth for consumers as it just drags out the whole process”.

However, consumers should still submit claims. David Kuo of fool.co.uk , the comparison website, said: “The law allows you to reclaim unfair charges plus interest that occurred in the past six years. As each day passes, it’s another day that you may not be able to claim for once the case is settled.

"Therefore, write to your bank to ask for the charges to be refunded. Follow up with a letter threatening court proceedings. Many courts will probably stay the majority of claims, but at least the six-year limitation on your claim will be halted.”

Many bank customers had successfully reclaimed charges going back six years prior to the case, but refunds have been suspended at the county courts during the High Court case.

“The banks should do the right thing, throw in the towel and reimburse the customers they’ve been overcharging all this time,” said Vicary-Smith.

The banks have opposed the challenge from the OFT to protect the estimated £3.5 billion a year generated from the charges.