People with long-standing credit card debts are being encouraged to up their repayments after regulator the Financial Conduct Authority (FCA) introduced new rules to support them last autumn .
The guidelines state financial firms must now take greater responsibility over those at risk of 'persistent debt' - by providing them with advice on better, more manageable repayment plans.
This includes writing to those who've been in debt for more than 18, 27 and 36 months and encouraging them to make higher repayments where possible.
In some cases, banks could suspend cards if borrowers do not act by March 2020.
However, charity StepChange said that while encouraging people to meet more than just their minimum payments will, in theory, help many, there are concerns that the letters aren't clear enough.
It said that the letters from card providers vary so much that customers are being left confused about what will happen next March.
Its own pilot project suggested that few people had taken any action so far.
"This begs the question about whether that's because they haven't realised the importance of doing so, haven't noticed their firm's communications, or simply can't afford to pay more," said Phil Andrew, chief executive of StepChange.
"At this point, there may be significant numbers of people with hidden problem debt who are coping on a minimum payment basis, but could tip over into difficulty once higher payments are required."
In February 2018, the FCA ruled that from 1 September all firms would have to do more to better protect their customers from 'persistent debt'. This is when customers have paid more in interest and charges than they have repaid of their borrowing over an 18-month period.
It imposed the rules after it emerged that 4 million people were trapped in this cycle - with the average person paying £2.50 in interest for every £1 they owed.
Under the new rules, providers must encourage those who've been in debt for 18 months or more to up their repayments. They must send out a reminder after 27 and 36 months, too.
After three years, the company must offer the customer a way to repay their balance in a reasonable period.
They could also cut, waive or cancel any interest, fees or charges from that point for borrowers still struggling to repay.
