The Office of Fair Trading is to launch a fact-finding study into internet shopping as fears grow over whether consumers are being treated fairly online.

The watchdog's study, which will concentrate on four specific areas including music and airline ticket sales, will explore whether consumers are being adequately protected as Britain’s £18 billion online retail market continues to post explosive growth.

The investigation follows similar actions across the world, provoked by fears that regulations have failed to keep pace with the fast-moving e-tail landscape.

Underlining the sector's rapid expansion, Amazon.com , the world's largest online retailer reported a 20 per cent hike in quarterly sales to $2.28 billion this week, beating expectations, as customers used Amazon’s website to buy music, films and other products, in addition to books, its traditional market.

As he unveiled an exercise expected to last until spring next year, John Fingleton, chief executive of the OFT, said: "The internet is fast becoming a hugely important channel for consumers and businesses.

"Its rapid evolution means that we need to ensure that the consumer protection regime gives current and future users the confidence to realise the internet's potential for shopping."

However, lawyers suggested that the budget for the investigation might be better spent on highlighting to consumers the rights they already have when they shop online.

Mark Dewar, a partner at Simmons & Simmons, the law firm, said: "It would be helpful if the OFT focused on publicising, and encouraging suppliers to publicise, the rights that consumers have already - for example shoppers have the right to a "cooling off period" for online purchases.

"They also have the right to cancel the contract without penalty and an entitlement to a full refund seven days after delivery of goods, or in respect of services, seven days after agreeing to proceed with services."

Around 130,000 businesses in the UK now sell online, in a market representing about 2.5 per cent of all household spending, according to the OFT, which has the power to take action if it considers a market is inefficient or anti-competitive.

In the last five years, internet retail sales in the UK have risen by 350 per cent, compared with growth of just 20 per cent for all retail sales, the watchdog said. Last year, the typical online shopper spent £560 over the internet.

Amid growing concerns about online scams and security issues over processing payments online, the OFT will try to establish whether shoppers are aware of their online shopping rights and whether businesses understand the regulations they should adhere to.

The study will divide the market into four separate areas: domestic electrical goods, music sales (including downloads), airline ticket sales (including accommodation bought at the same time), and online auctions.

The OFT said it had chosen these sectors because they represent at least a third of all online spending.

As part of the study, the OFT will consult with businesses, trade bodies, consumer group and public sector organisations.

The explosive growth of online retail has raised concerns around the globe. Earlier this year, the US Justice Department said it was investigating possible price fixing in the online music industry.

It is thought the US probe will investigate allegations that music labels have colluded to fix the wholesale prices they charge online retailers such as Apple, which sells digital music through its iTunes website.

The action mirrored an investigation launched in December by Eliot Spitzer, the New York Attorney General, who subpoenaed music company records to search for information on the prices they charge online vendors.

Last year, Steve Jobs, Apple's chief executive, accused the music industry of being "greedy" for wanting to raise digital download prices.

But Apple has also been criticised for its dominant position in the music market.

In some territories the company accounts for 80 per cent of online sales. In moves designed to open the market to competitors, lawmakers in France have sought to open up the closed link between the company's online music shop, iTunes, and the iPod, its music player.

The proceedings could eventually see Apple abandon the music market in France.

Consumer groups in Australia have recently complained that users of online music sites have to pay as much as three times as much as they should to download tracks over the internet.

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