Consumer group Which? has accused the UK's Payment System Regulator (PSR) of letting banks off the hook by not forcing them to reimburse customers who fall victim to online money transfer scams.
Which? had raised the issue with the regulator earlier this year, concerned that consumers had no legal right to claim money back from their banks in such circumstances.
The PSR subsequently launched an investigation and published an action plan. But while the regulator stated that banks must do more to prevent these scams happening in the first place, must produce better data around reports of scams and must react quicker to help consumers recover losses, it stopped short of making banks legally liable for any financial loss.
The PSR has "let banks off the hook" said Alex Neill, managing director of Which? home and legal services. "The outcome for people is unfortunately that they will continue to be scammed out of millions of pounds. We need to see swift action and not see this kicked into the long grass in the second half of 2017."
The consumer body has long argued that UK retail banks have failed to keep up with changing consumer habits, notably the increasing number of bank transfers - more than 70 million a month compared to 100 million in a whole year. In addition, many of these transfers are done electronically.
Which? launched a reporting tool in November and within two weeks had more than 650 victims reporting losses of more than £5.5 million from money transfer scams.
Banks have countered that many of the vulnerabilities are beyond their control, such as the compromise of clients' personal data, and there are various legal obstacles when it comes to sharing crime-related data.
The banks have called for new powers for data-sharing and, along with the Financial Fraud Action group launched the Take Five campaign ealrier this year to urge consumers to think first before transferring money.
"There is no silver bullet," said PSR managing director Hannah Nixon. "Tens of thousands of people have, combined, lost hundreds of millions of pounds to these scams but the data we have seen so far is incomplete. We need a concerted and co-ordinated industry-wide apporach to better protect consumers and we need to start it today."