The campaigning organisation cites the example of Which? member Iain Richardson, who had more than £2000 looted from his account within 20 minutes of having his debit card stolen. Natwest turned down his fraud claim because his PIN was used to withdraw the cash. It said he must have been negligent, and when he appealed to the Financial Ombudsman Service (FOS) it also turned down his case.
Earlier this month, a judge ruled against a Halifax customer who wanted compensation for money taken from his account, because his PIN number had been used.
Chip and PIN is the most secure method of payment, but Which? says that a fraudster can discover and use someone's PIN by looking over their shoulder at a cashpoint or retailer terminal before stealing the card.
Card fraud at cash machines increased by 31% between 2007 and 2008, and around £609.9m was lost in the UK through card fraud last year.
The Financial Services Authority has been tasked with taking over retail banking regulation from this November, and Which? is expecting the watchdog to provide more detailed guidance on the evidence that should be provided by banks in card fraud cases.
Which? says it will be making representations to the FSA as it develops its new role in the coming months, "ensuring that the process is both fair and fully transparent for consumers".