Some High Street banks are charging "eye-watering" rates of interest when their customers go over their overdraft limit, research by Radio 4's Money Box programme has revealed.

A customer borrowing £100 for 28 days without the consent of Santander would repay £200, for example.

That is the equivalent annualised percentage rate, or APR, of 819,100%.

Eric Leenders, from the British Banking Association, said that the industry was willing to look at concerns.