Online shoppers "have more rights" than people browsing the High Street, so long as any returns are made within 14 days, the head of a consumer watchdog told Good Morning Britain.
Executive director of Which? Richard Lloyd also said safe delivery was the responsibility of the retailer not the postal service.
Internet shoppers have been warned about the increased risk of being swindled by an fraudster ahead of busiest day of the year for online sales.
Online bargain hunters are urged to install "basic security protection" and be wary of who they give their credit card details to.
Giovanni Ruberto, online security expert at Intel Security, said:
UK shoppers will hit the web today with £650 million expected to spent in online sales as Cyber Monday kicks off.
Retailers are continuing the pre-Christmas sales push with a new set of deals, and IMRG Experian predicts consumers will spend £649.6 million today, or £451,000 a minute - a 26% increase on last year.
However, no repeat is expected of Black Friday's chaotic scenes, as online shoppers can browse and buy from the comfort of their own home.
Internet shopping figures consistently peak on the first Monday in December, as a combination of payday and a weekend spent browsing shops leads bargain hunters online in search of the cheapest deal.
Website hits are expected to peak at noon, with 125 million visits to online retailers.
However, there are expected to be some losers to Cyber Monday - small businesses are often not on the internet making it difficult for customers to support local firms.
Research from the Department for Business, Innovation and Skills (BIS) said research showed that 55% because they did not have a website.
BIS said small businesses and sole traders could be missing out on total website sales in the UK worth £164 billion without a digital presence.
Payday and the arrival of December are the driving factors behind today's expected cyber shopping surge, according to Sage Pay, which has predicted spending of more than £500 million.
“With just four weeks until Christmas, most of us will just have been paid, so Cyber Monday is traditionally the day when consumers rush online to do their Christmas shopping, said Simon Black, chief executive at Sage Pay.
“Given the breadth of shopping and payment options available to consumers, competition between retailers is greater than it’s ever been.
"Plus, with an emphasis on omnichannel and a host of newer payment technologies beginning to make their mark, retailers can find it difficult to stay that one crucial step ahead of the trends.”
Online retailer Amazon is testing unmanned drones called Octocopters in a bid to deliver packages to customers within 30 minutes.
The drones could deliver packages that weigh up to 2.3kg but the service is not expected to start for at least five years, the company's chief executive Jeff Bezos claimed.
Mr Bezos told CBS television's 60 Minutes programme: "These are effectively drones but there’s no reason that they can’t be used as delivery vehicles...I know this looks like science fiction. It’s not."
"We can carry objects, we think, up to five pounds, which covers 86 per cent of the items that we deliver...These are electric motors, so this is all electric; it’s very green, it’s better than driving trucks around," he added.
The service will be called Prime Air but US aviation officials have not approved use of the drones.
As shoppers gear up for Cyber Monday, retail expert Kate Hardcastle says consumers can avoid Christmas shopping delivery issues by making themselves aware of retailers' delivery and dispatch policies before they buy.
"Make sure you look for things like 'dispatch on' and 'delivery by' - two very different things," the retail expert told ITV Daybreak.
- Online shopping is up 10.1% in 2013 compared to 2012, according to Barclaycard
- The first Monday in December last year was the highest day of online spend in Barclaycard's history - consumers spent an average of £57 per transaction
- Online electronic stores - up 66.5%, online family clothing stores - up 35.4% and online department stores - up 31.5%, saw the biggest increases in spending
- Visa Europe predicts £450 million will be spent on its cards alone
- Online transactions could top 7.7 million, an increase of 16% on last year
- An average of £312,500 is expected to be spent every minute, Visa said
- UK consumers will make 113 million visits to online retail sites today, online analyst Experian claims
Retailers are predicting online shopping transactions will peak this evening.
- The slots between 8-9pm are expected to be the busiest for both Visa Europe and John Lewis.
- Amazon.co.uk is expecting peak sales at 6pm.
- Last year on Cyber Monday, over 3.5million items were ordered on the site at a rate of around 41 items per second.
The busiest day of the year for online shopping begins as retailers brace themselves for "Cyber Monday".
It comes after last week's "Black Friday" - a day of flash sales designed to kick off the festive shopping season - arrived in the UK and was marred by violence.
Online shopping figures have consistently peaked on the first Monday of December over recent years, with Visa Europe predicting this year's Cyber Monday will be the busiest ever.
The payment service predicts £450 million will be spent on its cards alone as online transactions reach the 7.7 million mark.
Cyber Monday sales will have grown by 16% on last years, making it the busiest online shopping day in history.
Visa Europe director of commercial development, Jeremy Nicholds, explained: "With an average of £312,500 expected to be spent online every minute on December 2, the Christmas shopping season will certainly start with a bang."