Travel firms have been told they must stop hitting customers that use debit cards with hidden charges.
An investigation was launched into hidden surcharges by the Office of Fair Trading (OFT) after Which? launched a super-complaint into the issue earlier this year.
Travel customers often have to click through a number of pages online when ordering tickets before they are told of added charges.
But that practice has been outlawed by the OFT, which has today told firms that they must make all charges for debit and credit cards clear.
It also wants to see a change in the law which will ban all charges for using a debit card online, although companies will still be able to charge for credit cards, which can cost more money to process.
The OFT said that traders should stop charging for paying with any debit card as they are 'the online equivalent to cash' and is talking to the Government to implement a change in the law.
Firms that continue to hide charges have been warned by the OFT that they can expect action to be taken against them.
"We recognise that most traders want to treat their customers fairly," said Cavendish Elithorn, senior director of the OFT's Goods and Consumer Group.
"Many already meet the minimum standards we expect under the law and we have secured a clear commitment to change from others.
"However, we will take enforcement action against any businesses that do not respond to today's announcement and instead continue to use misleading surcharging practices.
"We believe there is also a strong case for a change in the law so that the cost of using a debit card, the almost universal payment method for today's online consumers, is always included within the headline price."
Prashant Vaze, head of fair markets at Consumer Focus, said the ruling was a victory for common sense.
"Consumers have rightly been baffled about the reasons why they are being asked to pay unreasonable charges when using debit cards, especially when they bear no relationship to the costs these companies actually incur.
"Customers want traders to be honest with them about costs from the start and not face hidden charges added at the end."
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