It also predicts that the VAT increase means that consumers will be making more big-ticket purchases online.
IMRG said that despite adverse weather conditions affecting postage, consumers would still shop online for the convenience it offers.
David Smith, managing director of IMRG, said that with many shoppers unable to get to the high street, online sales could see a boost over the next few weeks.
He said: "Christmas Day has become a busy online shopping day in recent years, as people with an eye for value look to take advantage of the 24/7 nature of online retail."
The predictions are backed by analysis from payments company Visa, which estimates that 960,000 transactions, worth £36m in total, will be made on Visa cards on Christmas Day.
Charities could see a boost in donations on Christmas Day too, as shoppers making savings click through to donate online, according to Mark Clark, marketing director at free fundraising site The GivingMachine.
Clark said: "Last year, we saw a staggering increase in ‘free’ donations as shoppers clicked via www.thegivingmachine.co.uk to make the most of Christmas Day and Boxing Day bargains."
According a recent YouGov and CyberBoxingDay.co.uk survey, 8% of UK adults plan to shop online on Christmas Day, while 15% intend to do so on Boxing Day, and 10% on Christmas Eve.
It also found that three in 10 adults in the UK plan to make online purchases over the Christmas period leading up to 4 January.
Last week, the Office for National Statistics (ONS) released figures showing that internet sales were at an all-time high, accounting for 10.5% of total retail sales in the UK for November.
Online sales rose 37.5% from October to November, with all retailing growing by just 10.2%, according the ONS.