Helen Dickinson, the new director general of the BRC, said the "stand-out" online performance came after slower momentum in the previous few months.
She said: "Many valued the ease and convenience of shopping online during the Christmas period. The surging popularity of tablets and smartphones giving even better access is a major factor."
She also said shoppers felt much more comfortable putting their credit card details into their mobile phones.
More top news
Theresa May will make her pitch to lead the Conservative party today, 90 minutes before long-time favourite Boris Johnson.
Cool temperatures and breezy conditions with a top temperature of 20 Celsius (68 F).
Suicide bombers targetting Istanbul's airport incited panic to take lethal advantage in an attack that echoed the Brussels airport atrocity.