Online retail sales grew by 16% year-on-year in May despite tough sales comparables with last year’s Diamond Jubilee.

May sales were also up 5% on April, according to the IMRG Capgemini e-Retail Sales Index.

Conversion rates in the month jumped to 4.9%, excluding travel.

At the same time the average basket value from January to May, excluding travel, fell to £77 from £83 in 2012 and £86 in 2011. The Index said this could be due to online shoppers searching for bargains.

Capgemini vice president, head of retail consulting and technology, Chris Webster said: “The online sales reflect the ongoing economic climate.  Whilst there has been a slight growth in average earnings, it is still running behind the current rate of inflation of 2.4%; as a result Brits have to be savvier shoppers and embrace the savings that can be found online.”

By category, fashion sales increased 16% against last year as the summer weather triggered consumers to update their summer wardrobes. Sales across home and garden also grew, up 41% due to the warmer weather.

Etailers outperformed their multichannel counterparts with a sales increase of 18% year-on-year against physical retailers’ 16% online sales growth.

The Index recorded rocketing m-commerce sales, surging 148% year-on-year, although this is the lowest since the Index began.

ECommera mobile product manager Oliver Ripley said: Looking at [the mobile] conversion ratio the first five months of 2012 versus the same period in 2013, the average ratio has increased from 1.4% to 2.16% which shows that more and more investment is going to optimising digital retail services for mobile users. 

“It seems that mobile commerce conversion ratios are now very nearly at parity with desktop commerce conversion ratios.”