Cyber Monday Shoppers Warned Over Scams
Spending is predicted to soar by 31% on last year following the Black Friday weekend,¬†according to Experian-IMRG.
But shoppers have been urged to be vigilant, as hackers are expected to be out in force targeting eager bargain hunters.
Cyber security expert Dave Whitelegg¬†said: "Lots of breaches occur months after credit and debit card details have been stolen.
"People scouting around for cheap deals may end up on scam websites. It's best to stick to reputable, well-known companies. If the price seems to good to be true, it usually is."
The amount spent online on Cyber Monday is expected to fall short of Black Friday's predicted spending of ¬£1.07bn - the first time that online retail sales in the UK were thought to have surpassed ¬£1bn in one day.
Spending online and in-stores over the four-days was expected to hit ¬£3.49bn, said the Centre for Retail Research.
Amazon reported record figures on Friday, with more than 7.4 million items ordered, leading to its biggest sales day ever in Britain.
But the predicted chaos on the high street failed to materialise, with shopper traffic down by 4.05% on last year, according to retail experts FootFall.
Consumer analyst Richard Hyman said: "Last year I think the industry embraced Black Friday with tremendous enthusiasm and dived in. This year it's been more muted."
Retailers which saw their websites struggling to cope with the volume of traffic on Friday will be hoping to avoid a repeat of problems today.
The John Lewis website went down at around 3.20pm, with one IT analyst estimating the company could have lost ¬£2.8m
Shoppers using the Argos, Tesco, Boots, River Island and Debenhams sites also reported problems.