Consumers could be about to spend their way to the UK's first £1 billion online shopping day as retailers brace themselves for Black Friday.

Retailers have been bombarding registered shoppers with emails detailing deals today ahead of them becoming available from midnight, while many stores are preparing to open their doors early.

Tesco and John Lewis are both installing queuing systems in expectation of large crowds, while the supermarket giant has assured customers it will have enough security and stock in stores following scuffles over limited numbers of items last year.

Ebay is expecting nine million Britons to visit its website over Black Friday, John Lewis has promised to honour its Never Knowingly Undersold pledge and match competitor's prices and Amazon.co.uk is promising significant bargains tomorrow after a week of early sales.

Argos is offering deals on more than 350 items from 1am online, including £220 off an LG 49in TV, £80 off a Toshiba Celeron laptop and a £70 saving on a Tassimo coffee machine. Superdrug is heavily discounting skincare, electric toothbrushes and perfume.

Currys PC World said it was expecting to take up to 10 online orders every second.

Deals include £500 off LG 60in 4K TVs, laptops, tablets and cameras with more than a third of the price off and 75% off the price of pay as you go mobile WiFi.

AO.com revealed a range of deals that it made available tonight, such as up to £450 off televisions, a Jura Impressa coffee machine at half price and £120 off a Dyson multi floor vacuum cleaner.

The online electricals retailer said prices could change, but would only go down rather than up, adding that all deals were on a "when it's gone, it's gone" basis.

Police have warned shops to ensure they have carefully thought-out security plans in place for the sales following chaos at a number of stores across the UK last year when huge crowds grappled for cut-price televisions and other big-ticket items.

Experian-IMRG believes internet spending on Black Friday will hit £1.07 billion, a 32% increase on last year's £810 million - the first time that online retail sales in the UK will surpass £1 billion in one day.

The Centre for Retail Research expects a slightly more modest £966 million online, but predicts total Black Friday sales including at bricks and mortar stores will reach £1.39 billion, with shopping over the entire weekend - culminating in Cyber Monday - to hit £3.49 billion.

Visa Europe predicts that shoppers will spend £721 million online on its cards on Friday, up from £616 million last year.

But while stores prepare their websites and distribution centres for unprecedented demand, consumer advocates warned that shoppers should exercise caution amid the rush for bargains.

Martin Lewis, founder of MoneySavingExpert.com, has warned that the majority of Black Friday deals "aren't special" and advised shoppers to cross-check deals with items they actually need.

He said: "Above all, remember: if you don't want something, don't need it or can't afford it, then don't buy it."

Which? urged shoppers to be prepared by registering for alerts from favourite retailers, searching for regular prices ahead of time in order to spot genuine bargains and to be aware that many deals are already available online.

It also warned that many websites slowed to a crawl last year, and suggested consumers register for online accounts early to "get in and out as quickly as possible".

Which? editor Richard Headland said: "There will be a whole host of deals available on Black Friday, but not all of them will be genuine."