Holidaymakers are shelling out an estimated £265,000 a day - £100 million a year - in unfair debit card fees charged by airlines, despite a government ruling which bans airlines from this practice.
Consumer watchdog Which? is calling on the government to tighten up the law to make it impossible for airlines to implement the charges.
It criticises airlines for continuing to make these levies, saying can leave a leave a family of four with a bill of £48 for one holiday.
In June, the Office of Fair Trading ordered companies to stop implementing extra card charges, but many airlines are simply refusing, and, at the moment, the ruling can only be enforced through the High Court.
According to the Which? research, budget airlines are among the worst offenders. And it says that two airlines - Swiss and Lufthansa - have even announced plans to start charging customers £4.50 for using debit and credit cards despite the OFT ruling.
Which? estimates it costs only 20p for a company to process a payment on a debit card and is calling on the government to make a 'minor change to the law' which would make it illegal for companies to levy debit card charges.
Richard Lloyd, executive director of Which?, said: 'It's time for the government to put a stop to this. A minor change to the law is all it would take to ban the charges on debit cards that you only find out about at the end of a lengthy online booking process.'
He said thousands of people had complained to us that these hidden card fees are unfair. 'The government must act so that consumers can easily compare the cost of their flights,' he said.
Yesterday, the OFT warned airlines it will take them to the High Court if the debit card surcharges do not stop.
Ryanair charges £6 per person per journey, which adds £48 to the cost of return flights for a family of four, athough there is no charge if a customer pays with a Mastercard Prepaid card. Easyjet, charges £8 for a whole transaction.