Shoppers are set to spend a total of £1.2bn on last minute gifts and groceries on what has been dubbed "Panic Saturday".
Around 13 million consumers will spend £2.1m for every minute stores are open at an average of £92.31 per person, according to a report by the Centre for Retail Research (CRR) for Vouchercodes.co.uk.
Claire Davenport, Vouchercodes.co.uk managing director, said: "With Christmas Day falling later in the week this year, consumers feel that there is still plenty of time to complete their shopping.
"Panic Saturday kicks off a big week for retailers and we're expecting to see a huge increase in traffic to our site this weekend."
Some of the biggest high street names have slashed their prices for what is expected to be one of the busiest shopping days of the year.
Debenhams has reduced some gifts by 50%, Boots is offering a 60% discount of selected fragrances, while Marks & Spencer is selling some beauty products for half-price.
Delayed online orders, poor weather and earlier sales are expected to drive around 70 million shoppers to the high street between now and Christmas Eve - an increase of 14% on last year.
The CRR report also predicts in-store sales will reach £4.74bn over the five days before Christmas, another noticeable increase on last year (21%).
The CRR says the additional shopping day will contribute an extra £870m.
Department stores can expect to double their takings this weekend, data from payment processing company Worldpay suggests, with shops in the north of England set to benefit the most.
It said the number of card payments taken by department stores in some parts of the UK just before Christmas increased by as much as 224% this time last year, and even better figures are expected for 2014.
Worldpay UK managing director Dave Hobday said: "Department stores are magnets for shoppers who find themselves in the last-chance saloon in the final few days before Christmas.
"Many of these eleventh-hour shoppers will be breaking into a cold sweat at the thought of heading to the high street on the busiest shopping day of the year and praying for someone to take the pain away."
Gallery: Black Friday: Madness In The Shops
Yes, really. Shoppers have wrestled over a television. It has come that, people. "Black Friday" is in full swing in Britain and the stiff upper lip Brits are famous for has well and truly left the building. This photo was taken at an Asda in Wembley, north London
Britain's high streets, shopping centres and websites have been awash with discounts as more retailers than ever embraced US-style promotions, seeking to kickstart trading in the key Christmas period