Big-name retailers have been called out for advertising “fake sales” this Black Friday, with new Consumer NZ data revealing 77 per cent of products it tracked could have been purchased for the same price or less in the weeks prior.

Consumer NZ tracked seven popular household items over 10 weeks to see if they were as good a deal on Black Friday as advertised.

It found Farmers offered the worst Black Friday deals with no specials that were cheaper than pricing on offer at some point in the previous nine weeks.

Meanwhile, Harvey Norman offered the best discounts with three items cheaper on Black Friday than at any time in the nine weeks prior.

“Black Friday sales are all about putting the pressure on and saying you need to buy now, but our research shows Black Friday is not offering particularly large savings,” said Gemma Rasmussen, head of research and advocacy.

“The only way to discern meaningful bargains from bogus promotions is to do your research.

“Terminology around sale pricing can be very persuasive, but sometimes it can be smoke and mirrors. First and foremost, Black Friday is a wildly successful marketing tool.”

Consumer found Farmers offered the worst Black Friday deals.

Black Friday specials which were available for cheaper in the weeks prior include the Delonghi Icona Kettle sold for $199.99 at Noel Leeming on Black Friday, but it could be purchased for $139.99 on September 25, and $159.99 on October 16.

Harvey Norman sold the Oral B 7000 electric toothbrush for $149 on Black Friday but September 25, it was on sale for $144.

Some retailers were notorious for always promoting a special.

“Across the 10 products we tracked at Harvey Norman, nearly every single one, every single week, was promoted as a ‘deal’ of some kind.”

But Rasmussen says, according to the Fair Trading Act, a special offer should be just that – something special or unusual.

“Black Friday marketing gives the impression that discounts are available for a limited period of time. But if a deal is ‘hot’ one week, it’ll probably be ‘huge’ or ‘great’ the following. Pause before you splurge is our advice.”

“Black Friday can be a great opportunity to purchase an item you’ve been coveting, but don’t trust retailers to let you know which deals are real.”

It comes as this Black Friday is predicted to rake in the biggest retail spend yet.

PriceSpy data shows the likes of laptops and home security cameras are predicted to cost 17 per cent more, while espresso machines will likely see an 11 per cent hike.

And with Kiwis expected to drop an average of $806 on deals - financial advisers are warning shoppers to spend cautiously.

“It’s like the Bermuda triangle of personal finance because you’ve got Christmas, you’ve got the holidays and then you’ve got back to school,” Sorted personal finance lead Tom Hartmann said.

“By the time you sail through all those things, it’s quite difficult to get through without having too much debt.”