More than 11 million people are set to spend in excess of £1 billion - at about £1.5 million a minute - on Saturday, with December 17 predicted to be the busiest shopping day of the festive season.
According to a report by shopping comparison website Kelkoo, consumers will spend £128 each on Christmas presents and other goods, taking the average family spend this festive season to almost £700.
Online sales are expected to soar by about 16% to £13.4 billion this Christmas compared to last year, however the high street is expected to see a drop of around 2%.
The report also said the number of pre-Christmas sales promotions could increase in the coming week if trade is poor.
Chris Simpson, chief marketing officer at Kelkoo, said: "The peak weeks of Christmas trading are crucial to retailers as this period accounts for nearly one-fifth of the UK retail industry's annual sales, making stores fight harder than ever to tempt shoppers through their doors.
"However, despite all of the high-street promotions and discounts that are already being offered, it's really important for shoppers who want to save money to check prices online before hitting the shops as many retailers operate a split pricing structure, whereby prices on their websites are lower than in their high-street stores."