Credit card companies must review how they treat customers who have been in persistent debt for 18 months, according to the financial watchdog.
The Financial Conduct Authority introduced rules in March 2018 requiring lenders to to help customers who paid more in interest, fees and charges than they have repaid on the balance on their card.
Firms were instructed to write to customers three times over a three-year period to reach an agreement to help them pay down debt.
The FCA said in a letter credit card firms that following a review of the rules, it was concerned that firms are proposing repayments options which are not reasonable, and even planning “blanket” suspension of credit cards.
“Where we identify poor practice, we will take swift action to ensure customers are being treated fairly and our rules are being followed,” said the FCA’s director of retail lending, Philip Salter.