A dangerous child car seat, a poor quality TV, a dodgy laptop and a washing machine that fails to get rid of stains are among the “dud” items being sold at discount prices this Black Friday, watchdog Which? has warned.

The consumer group warned shoppers that it had found items independently tested and deemed to be ‘don’t buy’ products included in the Black Friday sales across a number of major retailers including Amazon, AO.com, Currys, John Lewis and Littlewoods.

Which? found the ‘don’t buy’ Graco Junior Maxi child car seat discounted on Amazon, listed at £26 and marked as a “#1 Best Seller”, which – although legal to sell in the UK – was found to offer little side-impact protection in testing.

The watchdog said the “only thing worth praising” about the Hisense 55A7100FTUK TV, currently on sale at £419.99 from the recommended retail price of £559 at Littlewoods, was the remote, with testers describing the picture quality as “one of the worst 4K pictures we’ve seen”.

The Lenovo IdeaPad 3 14-inch 14DA05, which features on the Lenovo website as a Black Friday deal down to £269.99, had a “below par” screen, keyboard, touchpad, sound and battery life, testers found.

The Shark WandVac WV361UK was promoted as a Black Friday deal at AO.com and John Lewis at £169, down £30, but Which? expert reviewers found it was “terrible” at cleaning carpets, only removing around a quarter of the dust, and also “completely hopeless” at picking up pet hair during their tests.

At Currys, Which? found a ‘don’t buy’ Haier HW90-B14959S8U1 washing machine on sale at £409.99 instead of £450, but the consumer group warned it was not economical with water usage and they had found it ineffective at getting rid of stains on cotton clothes.

The Kenwood KMD70X19 fridge freezer, also on sale at Currys at £579.99, reduced from £629, was found to be too slow to cool, with an inadequate freezer, and could contribute to unnecessary food waste.

The findings follow Which? revealing that nine in 10 Black Friday ‘deals’ are the same price or cheaper in the six months ahead of the big event.

Which? head of home products and services, Lisa Barber, said: “A product that doesn’t do what it is supposed to is going to be a terrible deal, no matter how cheap it is – and this year we’ve found some absolute duds in the Black Friday sales.

“If you’re in the market for a quality product at a price that offers outstanding value for money, there are deals to be had, but we suggest you steer clear of these ‘don’t buys’ and seek out reliable reviews and independent testing that you can trust.”