Visa Europe predicts £518 million (€653 million) will be spent on its cards today, Black Friday, making it one of the biggest days for e-commerce.

It estimates that online transactions will top 8.5 million today alone, up 22 per cent on 2013.

Visa Europe is forecasting there will be approximately one million eCommerce transactions by Irish consumers on Visa debit, Visa credit and Visa prepaid cards between Black Friday 28th November and Cyber Monday, representing €74 million in purchases.

It said Irish online shoppers are set to spend €22 million on Monday 1st December, the busiest day for online shopping this year, which has been dubbed Cyber Monday. This represents a 17% increase on last year’s figures.

A shopping frenzy is already underway in the UK, and a number of retailers in Ireland are also offering heavy discounts.

"Black Friday is a signal to everyone to start thinking of Christmas promotions," Twitter's EMEA director small and medium sized businesses, Barry Collins, said.

Last year, almost 700,000 #BlackFriday tweets were posted on the day.

Over the course November 27-30, there were 3.7 million tweets mentioning Black Friday globally.

Mr Collins said there have been 100,000 mentions of Christmas on Twitter in Ireland in the last month. He said the peak day for mentions of Christmas will be December 23rd.

Meanwhile, a survey by Millward Brown has found consumers are using Twitter as a Christmas shopping tool, and the trend is growing.

The survey found 66 per cent of European shoppers follow an SME retailer or e-commerce site on Twitter, while 28 per cent of respondents said they are planning to use Twitter for Christmas shopping this year.

Almost 70 per cent of Twitter users said they had seen something on Twitter that prompted them to make a purchase.

A total of 44 per cent of respondents say they will be using social media even more than 2013 to help inform their Christmas shopping this year.