Analysis of last year’s prices show 39% of mobile phones and GPS, and 33% of computers and accessories were more expensive on 24 November (Black Friday) than they were on 1 November.

The data from product comparison site, PriceSpy, also found that 29% of games and consoles were cheaper in the weeks leading up to Black Friday.

Vanessa Katapa of PriceSpy said: “Unfortunately, some retailers inflate prices ahead of Black Friday to then drop them on the day making shoppers feel like they’re getting a bargain.”

The site surveyed 2,000 people and found that one in 10 assumed they were getting a good deal when a sale is on, while 37% compared the discount price to the RRP (recommended retail price), which tells you if you’re getting a discount but not if it’s the cheapest the item has ever been.

Ahead of this year’s Black Friday, which falls on 23 November, PriceSpy is urging shoppers to plan ahead and look at the price history of big-ticket items to ensure they are getting a genuine deal.