A list of companies have been named and shamed for hitting customers with "rip-off" surcharges, by consumer champion Which?.
The group has published a list of saints and sinners who it says implement a huge range of surcharges when consumers pay by credit and debit cards, with some hitting shopkeepers' pockets hard.
Which? previously ran a successful campaign pressuring the Government to ban rip-off card payment surcharges and the group has been monitoring how well the new rules are working.
Which? asked consumers if they felt they had been hit with a rip-off surcharge since the ban came into effect in April.
More than 700 people responded and researchers found that some companies were still charging excessive fees, with the worst offenders in the travel and holiday sector.
Which? said it believed several companies could be breaking the new rules.
It found eDreams was the worst offender and found examples of surcharges of more than 18% for customers paying by credit and even debit cards.
It also found easyBus, Vueling, Monarch, Jet2 and Germanwings were still charging over the odds with fees ranging from 2.5% to 3.5%.
The ban makes it illegal for companies to charge more than the cost to process payment.
Which? believes that this should be no more than 2% for credit cards and a matter of pence for debit cards.
Following complaints from consumers, Which? also contacted First Choice, Thomson, easyJet and Mytrainticket which all subsequently agreed to reduce their credit card fees to 2.0%.
EasyCar has gone even further and abolished all its fees for credit and debit cards.
Which? executive director Richard Lloyd said: " It's disappointing that six months after the Government banned rip-off surcharges, consumers are still being hit with high fees simply for paying with a card.
"While some companies have reduced their surcharges, there should be a crackdown on rogue companies who continue to flout the ban. We'll be passing on our findings to Trading Standards and asking them to enforce the rules."
Consumer Minister Jo Swinson said: "We know it can often be a nasty surprise when consumers see an advertised price and then have an excessive payment surcharge added at the end. This is why we brought in measures - a year earlier than required by European law - to make sure that UK consumers benefit from clearer and fairer prices.
"The prices that businesses charge should always be transparent. They shouldn't keep extracting more money from excessive administration or booking charges from customers with each transaction. Enforcers such as Trading Standards, the Office of Fair Trading and the Civil Aviation Authority have the power to seek civil injunctions against traders who break the rules on excessive payment surcharges. I will be writing to all the enforcement agencies about their obligations."
Sir Stelios Haji-Ioannou, chairman of easyBus, said the report was " misguided" and its average fare was about £6 with early bookers paying as little as £2.
He said: " Uniquely amongst our competitors, some 90-95% of our bookings are made online in advance and paid by credit/debit card.
"Our competitors still take most of their revenues cash in hand to the driver. No wonder they don't focus on credit card fees.
"EasyBus currently charges 50p per debit/credit card transaction compared with an approximate cost of 35p. It is astonishing that a 15p margin can be regarded as a 'rip-off' when easyBus undercuts alternative providers by half. This is a storm in a teacup over 15p.
"Which? clearly needs to rethink its raison d'etre."
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'Rip-off' surcharge companies named
Using a mobile phone to make and receive calls, send texts and browse the web while abroad can be extremely costly – especially if you are travelling outside the European Union (EU), where calls can cost up to 10 times as much as at home.
To avoid high charges, Carphone Warehouse suggests tourists ensure a data cap is in place, use applications to check data usage, turn off 'data roaming', avoid data-intensive applications such as Google Maps and YouTube and use wi-fi spots to update social networking sites.
Payment Protection Insurance (PPI) is supposed to help people to continue meeting their loan, mortgage or credit card repayments if they fall ill or lose their jobs. However, policies are often over-priced, riddled with exclusions and sold to people who could not make a claim if they needed to.
At one point, sale of this cover - which was often included automatically in loan repayments - was estimated to boost the banks' profits by up to £5 billion a year.
Now, though, consumers who were mis-sold PPI can fight back by complaining to the bank or lender concerned and taking their case to the Financial Ombudsman Service (08000 234567) should the response prove unsatisfactory.
It could be you, but let's face it, it probably won't be. In fact, buying a ticket for the Lotto only gives you a 1 in 13.9 million chance of winning the jackpot.
With odds like that, you would almost certainly be better off hanging on to your cash and saving it in a high-interest account.
No-frills airlines such as EasyJet may promote rock-bottom prices on their websites. But the overall fare you pay can be surprisingly high once extras such as luggage and credit card payment fees have been added - a process known as drip pricing.
Taking one piece of hold baggage on a return EasyJet flight, for example, adds close to £20 to the cost of your flight, while paying by credit card increases the price by a further £10.
It may therefore be worth comparing the total cost with that of a flight with a standard airline such as British Airways.
Cash advances, which include cash withdrawals, are generally charged at a much higher rate of interest than standard purchases.
While the average credit card interest rate is around 17%, a typical cash withdrawal of £500, for example, is charged at more than 26%.
What's more, as the interest accrues from the date of the transaction, rather than the next payment date, costs will mount up even if you clear your balance in full with your next payment.
Supermarkets such as Tesco and Asda often run promotions under which you can, for example, get three products for the price of two.
However, it is only worth taking advantage of these deals if you will actually use the products. Otherwise, you are simply buying for the sake of it, which is a waste of your hard-earned cash.
Buy a train ticket at the station on the day of travel and the price is likely to give you a shock - especially if you are travelling a long distance at a busy time of day.
However, you can cut the cost of train travel by 50% or more by going online and making the purchase beforehand - especially if you book 12 weeks in advance, which is when the cheapest tickets are on sale.
Other ways to reduce the price you pay include avoiding peak times and taking advantage of so-called carnet tickets, which allow you to buy, for example, 12 journeys for the price of 10.
Most High Street banks offer packaged accounts that come with monthly fees ranging from £6.50 up to as much as £40, with a typical account charging about £15 per month.
Various benefits, such as travel insurance and mobile phone insurance, are offered in return for this fee. But whether or not it is worth paying for them depends on your individual circumstances.