It believes many of the UK's 62,000-plus internet traders are not aware of their responsibilities either.

The warning comes as part of National Consumer Week, which this year focuses on "buying from afar".

One study suggests that the total amount spent by UK consumers online may reach as much as Ј40bn this year.

Online boom

The Trading Standards Institute was drawing on detailed research carried out by the Office of Fair Trading (OFT).

It highlighted the growing scale of internet trading, but found that buyers lacked knowledge about their ability to cancel an order, how to get a refund and how to check that online traders meet legal obligations.

Businesses were also not always clear about their responsibilities, while some did not adequately address concerns about privacy and security.

"The findings demonstrate the urgent need to improve awareness among shoppers and sellers and to highlight the danger signs", said Ron Gainsford, chief executive of the Trading Standards Institute.

The price comparison website uSwitch estimates that online shopping in the UK will rise to Ј40bn this year, fuelled by cheaper broadband deals and faster connection speeds.

"The internet is a fantastic marketplace for UK shoppers," said Christine Cryne, director of consumer direct at the OFT.

"But consumers could do more to find out about their rights and get themselves a better deal," she added.

Online shoppers are being directed to Consumer Direct, the free telephone and online service funded by government, which offers information and advice about customers' rights.

Additional rights

The OFT issued new guidance setting out firms' responsibilities earlier this month.

Under the Distance Selling Regulations, consumers who buy online or over the telephone have more rights than consumers who buy on the High Street. In most cases they are entitled to a seven-day "cooling-off" period.

Sellers must provide clear written information about the goods or services in question.

This must specify their contact details, a breakdown of costs, including any relevant taxes and delivery charges, and details of how to cancel an order.

Some products and services are not covered by the rules, such as personalised items or perishable goods such as flowers or fresh foods. Financial products are covered by different regulations.

Local trading standards offices are responsible for enforcing the rules.

Source: news.bbc.co.uk