Several retailers, including B&Q and fashion houses Gap and Oasis, have all commenced "New Year" sales before Christmas at their high street outlets. Tesco has now joined the fray online.
Official figures for November show that 10.5% of all retailing is now done online, but this is expected to rise in December.
Tesco commercial and marketing director Richard Brasher predicted the grocer would have its "biggest-ever" Christmas before the cold snap.
Brasher, today (23 December), said: "Our big-brand sale will be a firm favourite with our customers who look for bargains on electrical, homeware and entertainment products. Many of our customers want to get ahead and shop online from now.
"Christmas Eve and even Christmas Day will be two of Tesco’s busiest online shopping days this year. Only Boxing Day will be busier."
Tesco will add to its list of discounted items on Christmas Day.
Eager shoppers crashed Tesco's Clubcard website in early December, trying to take advantage of a deal to multiply Clubcard points before the offer closed.
Earlier this month, independent grocers complained that the takeover of Mills stores by Tesco subsidiary One Stop should be referred to competition authorities.