British banks have charged current account holders a staggering £4.7 billion in overdraft charges over the last year, new research revealed.

Consumer magazine Which? discovered customers who exceed their authorised overdraft limits are charged on average penalties between £20 and £30.

Account holders were also charged a further £25 to £30 for standing orders, direct debits or cheques paid out while they were in the red.

The study found HBOS, the Royal Bank of Scotland and Natwest imposed the highest charges for customers going £50 over their £250 overdraft limit for three days – each imposing a £118 penalty.

Abbey charged the second-highest penalty for the same scenario, at £110, and Northern Rock, the lowest at £28.

"It's time for banks to start treating their customers fairly by reducing their excessive charges for unauthorised overdrafts and credit cards," Which? said in the report.

"Charges should cover only the banks' true costs of dealing with late charges and exceeding overdrafts."