A major new set of consumer rights has come into force giving online shoppers greater protection against hidden fees, charges and other pitfalls.
The EU Consumer Rights Directive means consumers can no longer be charged high fees for buying online with their debit or credit cards and extends the "cooling off period" from seven working days to 14 calendar days during which they can cancel an order and receive a refund without giving a reason.
Those buying music, films and books in digital format can also use the cooling off period for the first time.
Retailers must not supply the content within the 14 day cancellation period unless the consumer has given their express consent to this happening, and the consumer must also acknowledge that once the download starts they will lose their right to cancel.
The directive also bans all hidden fees and charges, with sellers obliged to include any extra amounts before the customer places an order.
Retailers will be banned from charging card fees that exceed the actual cost of processing a payment and companies operating a helpline will be banned from charging more than the basic rate for calls.
There will also be a ban on pre-ticked boxes in online purchases, meaning that traders offering add-ons will no longer be able to tick them in advance and customers will not be forced to actively opt out.
Which? executive director Richard Lloyd said: "The Consumer Rights Directive will give people greater protection against rogue traders and strengthen their rights when shopping online.
"As part of this new directive, companies and public bodies will also have to provide basic rate numbers for all customer service and complaint telephone lines, which is a win for the 88,000 people who supported our Costly Calls campaign.
"These changes, coupled with the new Consumer Bill of Rights, will give people more power to challenge bad practice."
Consumer minister Jenny Willott said: "What we want to see are empowered, savvy shoppers who know their rights, look around for the best deals and drive competition.
"Our research shows consumers are generally pretty good at this and know the law.
"But we do recognise it could still be easier to navigate, which is why we are simplifying the law through the Consumer Rights Bill.
"The reality is that people face many daily issues when exercising their consumer rights that could help them get a better deal, whether they have a faulty fridge or internet service.
"When something goes wrong you should speak to the business in the first place as this can be the quickest and easiest way to get it fixed.
"However, if this doesn't work, there are a whole host of consumer bodies, such as Citizens Advice, who can give advice and get you your money's worth."
Citizens Advice chief executive Gillian Guy said: "People should not be losing hundreds or thousands of pounds because firms flout the rules.
"Consumer confidence is an important part of a continuing economic recovery.
"It's really important that consumer protections are working effectively to make sure shoppers feel confident buying the goods and services they need, and that firms behaving badly aren't getting a competitive advantage over traders who are doing the right thing."