The organisation, whose members include everyone from Tesco to Argos, Ikea and Lastminute.com, says UK shoppers will spend �17bn online this year.

And as purchasing over the web becomes ever more popular, it estimates that this figure will rise to �80bn by 2009.

The IMRG's members said retaining their customers was now their key priority.

Better security

In 2003 customer confidence topped the IMRG's priority list, but this has fallen to number 12 for 2004, suggesting that consumer faith in internet trading has greatly increased over the last 12 months.

The report said increased payment security was a main reason for this growth in confidence.

It also found that UK customers are leading Europe when it comes to shopping online - 27% of Britons have now bought over the internet, compared to 16% on the continent.

Laura Wade-Gery, chief executive of Tesco.com, said its own user figures matched those of IMRG.

"You only have to look at the business we did last December to see how fast we're growing," she said.

"We did as many sales in December as we did in the whole of 1998."