Kindle tablet
UK consumers are using tablets more often for online shopping with mobile devices accounting for £3bn of e-retail sales in 2013Reuters

Britons spent £91bn shopping online in 2013 as the e-retail sector continues its robust growth.

This is a 16% increase on the previous year's spend and online shopping now accounts for more than a fifth of the total retail market.

That's according to the e-retail sales index compiled by IMRG, an industry body for e-retailers, and consultancy specialist Capgemini.

"This performance has been fuelled by a variety of factors, not least the huge leaps in mobile technology, which has given a whole new section of society access to the internet and enabled the more tech savvy amongst us to shop while on the move," said Chris Webster, head of retail and technology at Capgemini.

"Combined with greater choice of delivery and collection options, as well as improved retail trading, the e-retail sector has all the ingredients for on-going success."

He added: "What we see is an acceleration of the rate of growth. One would think that as a market matures, the rate of growth would slow as the exponential growth tails off."

Webster predicts that e-retail could make up 30% of the whole retail market by the end of the decade.

The proliferation of mobile devices in consumers' hands, including smartphones and tablets, has driven up online sales. People use these devices to shop on the move, such as when commuting, or in the comfort of their own homes.

This sent sales from mobile devices soaring by 138% in 2013 when compared with the year before. These are now worth £3bn of overall retail sales.

The IMRG/Capgemini index forecasts online sales to rocket another 17% in 2014 and hit £101bn.

Christmas was also a strong period for online sales, rising 18% on the year before in December to an £11bn total.

"Our customers continue to evolve how they shop, and are increasingly blending stores, online and mobile devices," said Mark Lewis, online director at the John Lewis department store chain.

"With strong results from our shops as well, December 2013 was a truly omni-channel Christmas."

In the five weeks to the end of December, John Lewis's online sales jumped 22.6% on the same period a year before. They account for 30% of all sales, a 5% increase on 2012.

Mobile devices now account for half of all traffic to the John Lewis website.