Video report by ITV News Correspondent Peter Smith
Only one in 20 Black Friday "deals" are cheaper during the sale than at other times of the year, consumer group Which? has found.
Ahead of this year's annual sales, the consumer group said it found "few genuine discounts" after monitoring the price of several items throughout the year.
Which? tracked the prices of 38 products that were on sale on Black Friday last year - starting six months before the day and six months after.
Scroll down to check out the best tips from consumer group Which? on how best to grab yourself a bargain during the sales.
Which? looked at deals from retailers including Currys PC World, Amazon and John Lewis and found that just four (5%) of products were cheaper during the Black Friday sales than at other times in the year.
Which? found that six in 10 (61%) of the products on offer - which included speakers, soundbars and kitchen appliances - were cheaper or the same price on at least one day in the six months before the annual sales event in November last year.
When looking at the two-week period surrounding Black Friday itself - including sales prices in the week before and after - Which? found that three quarters (74%) of products were cheaper or the same price in the six months after.
While Which? said there was no evidence that retailers were breaking the law, they said they were worried that shoppers risked being confused by offers that may not be as good as they sound.
It has been urging shoppers not to get carried away and take their time to research properly.
Examples of Black Friday "deals" Which? found include:
A Samsung HW-MS650 soundbar was £299 at Currys PC World on Black Friday, but within a month the price dropped by £49 for at least five days. Which? found it was priced at £279.97 at least 13 times in the six months after Black Friday.
A DeLonghi Autentica Cappucino Bean-to-Cup coffee machine was priced at £399 by John Lewis on Black Friday. It was cheaper on at least 64 days in the six months after, including being priced at #368 on at least 35 occasions.
An Amazon Echo (2nd Gen) (Smart speaker with Alexa - charcoal fabric) was on offer at £54.99 (39% off) on Amazon but it was cheaper on at least 13 occasions before Black Friday.
An Indesit IDC8T3B tumble dryer from Currys PC World was £20 cheaper than its "sale price" of £199 just two weeks before Black Friday.
Natalie Hitchins, Which? head of home products and services, said: "We have repeatedly shown that 'deals' touted by retailers on Black Friday are not as good as they seem.
"Time-limited sales can be a good opportunity to bag a bargain, but don't fall for the pressure tactics around Black Friday.
"Our investigation indicates that this popular shopping event is all hype and there are few genuine discounts."
Here are Black Friday tips from Which?:
Don't impulse buy - Work out what you need or want to buy and how much you're prepared to spend before you start shopping in the sales.
Don't panic - Don't worry about missing out on a good offer as Which? research has revealed that you could be better off waiting until after Black Friday anyway.
Find out about offers in advance - Sign up to your favourite retailers' newsletters for inside tips, or check their social media pages ahead of the sales for any clues or hints to what will be on offer.
Look at the price on previous days, using websites such as PriceRunner, to make sure you really are getting a good deal.
Don't always trust reviews you find online - a recent Which? investigation found shoppers risk being misled by fake online product reviews.
In response to the Which? research, an Amazon spokesperson said: “The claim from Which? with regard to Echo is false and we have made this clear in our response to them.
"Amazon.co.uk customers were not able to buy the Echo (2nd gen) device cheaper before Black Friday 2018."