The OFT has told card companies to halve their charges
Bank and credit card customers should challenge charges they feel are unfair, a leading consumer group has urged.
Emma Bandey of Which? told BBC Radio 4's Money Box current charges are disproportionate and in breach of consumer regulations.
Ms Bandey spoke of the group's delight with the Office of Fair Trading (OFT) announcement on Wednesday which said credit card charges must halve or companies could face legal action.
The OFT said the fines - imposed when a payment is missed or a credit limit breached - should only cover certain limited business costs.
It set a "threshold for intervention" at £12, above which point it will presume the charge is unfair.
Ray Hall, director of enforcement at the OFT told the programme: "The default charges they are setting are not legally fair. They have been set at too high a level."
The OFT said its principles also apply to other contracts such as those for bank overdrafts, but no "threshold" has been set for these yet.
Ms Bandey urged people to contact their bank if they do incur a fee and "take a note of who you speak to and the date you speak to them".
She added: "By law you can challenge charges up to six years previously. Banks and credit card companies are obliged by law to give this information. There may be a small fee of up to £10, but you can write for this information.
"All charges in this six years, you can make a claim back on them."
Mr Hall also had advice for consumers.
"There is absolutely no reason why consumers should not question a bank about the basis on which a default charge is being set," he told the programme.
"What we would not want to do is encourage consumers to breach their contract by refusing to pay a default fee.
"If they have serious concerns about it and feel they are not getting a satisfactory response from a bank, I feel the right course for them is to seek their own legal advice."
Joanna Elson, executive director of the British Banker's Association, denied members' charges were unfair.
"We think our charges are fair, transparent and legal and we are rather perplexed by the OFT's announcement, particularly applying the principle that they have applied to credit cards to other products," she said.
She said the banks are in dispute with the OFT over the credit card figures, and added: "As far as we are aware they have not spoken to anybody about the costs involved in the other products."
Banks and credit card companies point out that charges can be avoided if customers set up direct debits to ensure payment dates are met, and keep a close eye on their accounts.
BBC Radio 4's Money Box was broadcast on Saturday 8 April and was repeated on Sunday 9 April at 2102 BST.