Sales during December are expected to rise 4% year on year to £42.4bn, with shoppers predicted to spend more than £1.5bn than last year.
Analysis by Deloitte also predicts online will account for 13% of sales and 50% of market growth.
Click & collect is also expected to account for 45% of all online transactions - almost double the level seen in December 2013 - with £2.5bn worth of sales.
Digital would influence 40% of physical shop sales, said Ian Geddes, head of retail at Deloitte.
“Growth in the influence of digital on physical retail has been driven by consumers’ desire to access information on products and services, compare prices and increasingly pay and transact via digital devices,” he said.
“As investment in in-store digital technologies increases, such as mobile payments to facilitate faster, more convenient transactions and beacon technology to track shoppers in-store and deliver personalised messages and promotions, so will the digital influence on the physical environment.”
On click & collect, Geddes added: “Increases in sales won’t happen by default; they may require some adjustment of the in-store experience targeting customers that are clicking and collecting. However, the real winners will be those retailers that have invested in adapting their supply chain and warehousing to accommodate these changes in consumer shopping behaviour.”