Brits have been stung with a total £300m in unarranged overdraft fees in the past year, costing them an average of £33 each time.

The research by comparison site uSwitch found that 5% of those had been hit with fees in excess of £100 after spending beyond their agreed overdraft limit by about £60.

But almost half (46%) have called their bank to complain and nearly two thirds (62%) were successful in getting a refund of the charges. In other cases, its research revealed banks would only waive the fees once.

A fifth of complainants were offered options such as a balance reminder or a text alert to prevent them incurring further charges in the future.

However, a majority of those surveyed (67%) think their bank should let customers turn off their unauthorised overdraft facility.

This is not standard practice currently, and a quarter said when they contacted their bank they were told they were unable to deactivate their unarranged overdraft. A further quarter said they didn’t know this was even an option.

The table below shows the cost of an unarranged overdraft at various banks:

As such, uSwitch is calling on all banks to offer customers the ability to opt out of their unarranged overdraft, so they can avoid these costly charges and better manage their finances.

Tom Lyon, a money expert at uSwitch.com, said banks are raking in millions every year from unarranged overdrafts and failing to do everything they can to prevent customers from dipping deeper into the red.

“Consent and, ultimately, control over finances needs to be in the hands of consumers. Yet, too many are in the dark about whether they can turn off their unarranged overdraft facility and avoid these extortionate fees. If consumers would rather have their card declined at the checkout than be stung by sky-high fees, they should be given the option to do so.

“We urge banks to offer every customer the option to deactivate their unarranged overdraft. In the meantime, customers should contact their bank and set up text alerts for when their account balance is low, so they can take action before drifting into an unarranged overdraft. Overdraft costs vary widely between banks, so it also pays to compare all the options available to you and switch if you find a better deal.”