Borrowers dipping into their unarranged overdraft by £100 could be charged up to £156 more by some high street banks, compared with the maximum payday loans companies are allowed to charge.

The research from campaign group Which? compared the cost of borrowing £100 for 30 days and found that unarranged overdraft charges from some major lenders were as much as 7.5 times higher than the maximum £24 payday loans cap.

Of the seven major lenders – Barclays, Halifax, HSBC, Lloyds, Natwest, Santander and TSB – Barclays had the lowest fees (£29.75 and £59.50 over single and double charging periods) while Halifax had the highest over 30 days in a single charging period (£100), though Natwest charged the most over 30 days across two charging periods (£180).

In January 2015, the Financial Conduct Authority (FCA) introduced a cap on high cost short-term credit to protect consumers from excessive fees charged by payday loan companies.

As bank overdraft charges apply to a monthly billing period, rather than the number of days money is borrowed for, individuals who need £100 could pay up to £180 in fees if they borrow across two billing periods.

Which? is now calling for the regulator, the FCA, to use its High-Cost Short-Term Credit Review to crack down on “punitive” unarranged overdraft charges. It also said that banks which set their own monthly maximum charges for overdraft borrowing should not be able to charge more for unarranged overdrafts than they do for arranged overdrafts.

Vickie Sheriff, Which? director of campaigns and communications, said: “It’s not right that people with a financial shortfall can be charged so much more by the big high street banks than they would by a payday loan company – especially if the money is borrowed over two monthly charging periods. If banks can continue to set their own charges, then consumers will continue to be hit by exorbitant fees.

“The Financial Conduct Authority must use its current review to cap these high charges and ensure consumers cannot be charged more for unarranged overdrafts than arranged overdrafts.”

Halifax said unplanned overdrafts are designed for occasional spend and the vast majority of its customers do not use them while Natwest said it encourages customers to contact them if they are going to enter an unarranged overdraft regardless of the amount or the length of time as the bank may be able to put an arranged overdraft in place, where the costs are less.