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
A challenge to the decision not to take further action against Sir Cliff Richard over alleged sex offences has been dismissed.
Theodore Liang will launch his own fashion line next year while taking acting and dance classes.
Monarch has denied it is in financial difficulty on the verge of closing. But here is what to do if your airliner goes bust.