The Ombudsman's withering opinion of banks' responses to card fraud claims was obtained in a Freedom of Information request from consumer champion Which?. The lobby group found that three-in-five consumers from a total sample of 3000 had experienced fraud on their accounts, with victims losing £624 on average for credit cards and £677 for debit cards.

Almost all victims got their money back eventually, and most banks reimbursed 64% of card victims within a week. However, 29% of the poll were kept waiting between one and four weeks, with 7% waiting even longer.

Of disputes referred to the Financial Ombudsman, around one in four complaints relating to fraud and disputed transactions were upheld in the customers’ favour. Barclays/Barclaycard were ordered to pay up in 56% of cases whilst 47% of Santander customers were wrongly denied compensation, compared with just 22% for NatWest.

Which? executive director Richard Lloyd, advises consumers who are disatisified by their bank's response to a disputed transaction to escalate the complaint to the Financial Ombudsman.

“With fraud rates on the rise, it’s encouraging to see the vast majority of victims got their money back," he says. "Banks have a duty to resolve cases of fraud quickly and can only delay a refund if there is suspicion of wrongdoing.”

Bank-backed body Financial Fraud Action UK has leapt to the defence of the sector: “Banks take fraud extremely seriously and the FCA’s extensive review of fraud refunds published this summer found that, if they suffer fraud, customers are being treated fairly by their card issuers. The FCA also identified that firms err on the side of customers when they are reviewing a claim, and so it is good news that Which? has found that customers received refunds in almost all cases.

“Fraud cases can be extremely complex, so it can take time for a full investigation to take place into the specifics of an incident, however banks always endeavour to make the process as fast as possible.”