Online transactions topped 7 million for the first time on a single day last week, when shoppers spent £365 million on Visa cards alone.
Mega Monday, on 3 December, followed the prediction by Visa Europe that it would be the UK’s busiest online shopping day.
High street sales were also up on 2011.
Data from Visa Europe's Weekly Christmas Spending Tracker for the week of 3 to 9 December showed that spend is up 2.5% year-on-year as shoppers headed both online and in-store to stock up on festive purchases.
Mega Monday drives online sales up 4.4% year-on-year while the high street spending was up 1.9% year-on-year.
Dr Steve Perry, Commercial Director at Visa Europe, said:
“December’s arrival has really kick-started the countdown to Christmas as spending both online and on the High Street increased last week.
"Early December is typically a strong time for online shopping as consumers plan ahead to ensure their Christmas deliveries arrive on time, and we saw a new record number of transactions on Mega Monday, but the cold snap and festive cheer seem to have got people in the mood to hit the High Street too, with spend up 1.9% year-on-year.
“The data show that clothing retailers continue to benefit from an uplift in spend as people head to the shops to get ready for the Christmas party season.”
Clothing and footwear spending was up 11.3% week-on-week and 3.8% year-on-year, suggesting that people are looking to stock up on party wear and clothes as a Christmas gift.
Visa Europe's Weekly Christmas Spending Tracker uses adjusted Visa Europe card transaction data to provide a robust indicator of total consumer expenditure across all payment methods. With £1 in every £3 in the UK spent on a Visa card, the Tracker gives a uniquely comprehensive and timely insight into the health of consumer spending.