Dangerous electric heaters are being sold on major online sites, taking advantage of those trying to stay warm amid a surge in energy bills, Which? says.
The plug-in heaters have been found on Amazon, eBay and Wish and are being promoted by fake reviews and dodgy ads, according to the consumer watchdog.
Which? bought 10 plug-in mini heaters - some as cheap as £12 - and tested them in a product safety lab.
All of the models tested are illegal to sell in the UK and did not meet the Electrical Equipment Safety Regulations, leaving people at the risk of fires or electric shocks. Four of the 10 tested - three on eBay and one on Amazon - were found to be a fire risk.
Rocio Concha, Which? director of policy and advocacy said the products were illegal, could cause serious harm, and show that online platforms must do more to protect consumers.
She said: "The government must urgently legislate to strengthen product safety, including giving online marketplaces greater legal responsibility for unsafe products sold on their sites so that consumers are far better protected.
"Self-regulation of online platforms is simply not working. These platforms have put in place inadequate measures which leave consumers at risk. The government must give these platforms greater responsibility to protect people online."
Which? warned customers of several products that pose a serious risk, including the following:
Electric Portable Plug-in Heater
Listed product name on Amazon Lesvtu Electric Portable Plug-in Heater-Low Energy Mini Plug-in Wall Heater with Adjustable Thermostat and 12H Timer Led Display, Energy Efficient Small Ceramic Fan Heater for Office Home Room Bathroom
Issues: Counterfeit fuses, which didn’t contain the required ballast to stabilise the electrical current, were not present in the heater so posed a risk of electric shock, fire or even explosion. The plug failed to lock into place.
Plug In Wall Heater 500W
Listed product name on eBay Plug In Wall Heater 500W Mini Electric Space Portable Digital Timer Ceramic Heat
Issues: during the test, the heating element melted the plastic surround holding it in place.
Which? reported the heating element had slipped down within the product, creating another area of melting. It was also touching the outer grill, meaning touching the heater could result in electric shock or burns, and leaving it running could pose a fire risk.
Issues with both the internal and external build quality were also found. The grill at the front of the heater could be easily pulled away and the plug also posed a risk of electric shock.
Several versions of this heater sold on Amazon, eBay and Wish all failed, and Trading Standards also issued a recall notice for another model sold on eBay appearing to be identical.
Plug In Wall Heater
Listed product name on eBay Plug In Wall Heater Portable Mini Electric Fan 900W Space Warmer with Remote UK
Issues: Which? found the internal construction of this product to be so poor it poses a risk of fire or electric shock. Internal wires were badly soldered directly onto a circuit board, while another circuit board was just loose within the product.
It had a US-style plug, and there was a UK adaptor in the box. But the UK adaptor had no fuse in it and didn’t meet the UK standard for design either, posing a further risk of electric shock.
In response to the findings, an Amazon spokesperson said "safety is a top priority” at the company and all products are required to comply with applicable laws and regulations
"Two products were removed in December, including one in relation to safety concerns, and we have proactively removed similar items and introduced measures to prevent new products going on sale.
"We have removed the remaining two products while we investigate. If customers have concerns about an item they’ve purchased, we encourage them to contact us directly so we can investigate and take appropriate action."
An eBay spokesperson said: "We take the safety of our users very seriously. We had already removed three of the five listings that Which? flagged to us. One of the two remaining listings is selling a different product and the other one has already ended.
"We use block filter algorithms aimed at preventing unsafe products from being listed. These filters blocked 4.8 million listings in 2022 and are updated on a regular basis.
"On the rare occasion that an unsafe product does make it on to site, we swiftly remove it and provide product safety education to the sellers to prevent relisting."
Wish said in a statement: "Product safety is a top priority for Wish. The listing highlighted by Which? has been removed from our European platform, and we are monitoring for any identical or similar listings. We will take further action as appropriate."