The independent complaints investigator, the Financial Ombudsman Service, has revealed that in every case where a customer has complained about a rate increase, the card company has failed to prove the reasons for it.

As a result, borrowers have had their rate put back down. The FOS said that banks cannot simply say that the cost and risk of lending consumers money has increased by way of explanation.

A spokesman for the Ombudsman says: “We expect to see evidence that the card companies have actually assessed the borrower's risk.

“Whenever we ask to see this information, we find that the card company moves to a settlement quite quickly.”

Lenders would have to prove that the consumer has become a higher risk, and consumers would have the right to get the provider to prove this and see evidence.

The new Lending Standards Board - a voluntary code of conduct - formed out of the old Banking Code Standards Board, will oversee credit assessments and the prices charged by credit cards.