One in three of all U.K. online sales are now made on a mobile device, according to research by Interactive Media in Retail Group, the U.K.'s industry association for e-retail. The IMRG Capgemini Quarterly Benchmarking survey, carried out jointly with consulting firm Capgemini, covers the three months from November 2013 to January 2014.

Visits to e-retail websites via mobile devices now account for 45 percent of U.K. online traffic, IMRG says. M-retail accounted for 32 percent of U.K. online sales in the fourth quarter of 2013, an increase of 18 percent from Q3 2013.

Mobile commerce is particularly strong in the U.K. apparel sector, with 36 percent of online sales and 51 percent of website visits now coming via mobile devices.

Chris Webster, Capgemini's head of retail, believes the significant investments made in m-commerce sites have been an important factor in the growth of m-retail. The increase in m-retail transactions has also been supported by the growth of services such as click/reserve and collect, Capgemini said. Purchasing/reserving online and collecting in store now accounts for 25 percent of sales at multichannel retailers that have both an online and bricks-and-mortar presence, Capgemini says.

"With an estimated 12 million tablet devices sold in the U.K. alone last year, and 70 percent of U.K. consumers now owning a smartphone, it is not surprising that the penetration of mobile commerce has reached a third of the U.K. online retail market," Tina Spooner, IMRG's chief information officer, said in a statement.

"With mobile and tablets now accounting for almost four in 10 visits to e-retail websites and 27 percent of the U.K. online retail market, we expect growth to continue throughout 2014," Spooner said. "M-retail is set to account for 30 percent of online sales during Q1 2014."

According to IMRG and Capgemini, 27 percent of all U.K. online sales took place on a mobile device in December 2013, twice as much as in December 2012.