Fintechs in the UK have accused credit card issuers including NatWest and Barclays of “costing consumers millions” by not giving full access to their own data.

“Britain’s 14.5mn interest-paying cardholders [are] losing millions, if not billions, of pounds a year, at a time when their finances are already crippled by the cost of living crisis,” said Gavin Shuker, chief executive of credit card management start-up Cardeo, in a letter to City minister Andrew Griffith sent last week.

The letter reflects frustration among some fintechs who argue that if consumers were able to share their full financial data with them, they could better offer money-saving services including personalised spending insights, ways to manage credit card debt and cheaper payment methods.