Some banking consumers in the UK are paying over 800,000% APR interest when they go over their overdraft limit according to research by the BBC. If you’re a Santander customer and you dip into your overdraft without authorisation borrowing £100 over 28 days you would be required to repay £200, for example.

Believe it or not, that works out to be an equivalent APR of 819,100%. Of course, it is a bit unfair to compare the interest rate of an unauthorised overdraft with that of an agreed loan but it nonetheless illustrates the incredibly high cost of borrowing, despite all time base rate lows. Supporters of such high rates are not just banks but also consumers who have no need for overdrafts, siting the bank’s right to charge for the use of it’s money without permission.

Mike Dailly, from the Govan Law Centre, said: “What we’ve got here is banks with equivalent APRs of nearly one million percent, which is eye-watering.”

The maximum fee for borrowing £100 for 28 days from a UK payday loan company is £42 compared to £100 from a high street bank.

Those who think payday loan providers over-charge customers will be surprised to read that no such registered lender in the UK charged more than 5,000% APR, however Santander and Lloyds TSB charged an equivalent APR of more than 300,000%. Barclays were revealed to be charging an equivalent APR of 366,000% for 28 consecutive days in their ‘personal reserve’.

In a report last month, the Department for Business, Innovation and Skills (BIS) published a report on consumer credit saying that commitments made by High Street banks will “deliver a fairer, more competitive market and mark a real improvement for consumers”.

The cost of mis sold PPI and bank charges was brought into the spotlight back in 2009 when a Supreme Court ruling backed the banks saying charges were fair, but most of them did agree to reduce the level of their fees despite the victory. The problem now, if there is one, is that even though the charges have been reduced, the number of times a customer can be charged in one month has increased.

Interesting side note: The Office of Fair Trading (OFT) said the payday loan industry was worth about £115m in 2004, in 2010 Which? put that figure at £1.9bn. That’s a 17,000% growth in six years.