BBC TV's investigative series Panorama has discovered potentially dangerous child car seats for sale on Amazon's UK store.
The issue has been raised with Amazon, which says they have now been removed from sale.
Surrey Trading Standards first warned about these types of car seat in 2014.
Footage was released of a fabric car seat disintegrating during a crash test. The crash test dummy, representing a three-year old child, is shown being catapulted into the front of the car by the forces created during a 30mph crash. The fabric child car seat is ripped apart at the seams.
Our 2019 investigation also identified safety labelling issues:
Watch what happened in a crash test and find out more about why these seats are unsafe by watching our video from our 2019 investigation.
Sue Davies, head of consumer protection at Which?, says:
'It's extremely concerning that Amazon doesn't appear to have taken the basic steps needed to keep these potentially lethal car seats off the market, a year after we first exposed the serious safety issue.
'This is an issue that we've exposed time and time again across a whole range of products, and it's clear that consumer protections on online marketplaces are nowhere near strong enough.
'As the government looks to increase regulation of online platforms, it must make marketplaces legally responsible for preventing unsafe products from being sold on their sites.'
An Amazon spokesperson told the BBC:
'Safety is extremely important to us and we regret that these products were available from third-party sellers using our stores.
'After a thorough investigation, we identified the issue and are removing these products, and we're also contacting each customer who purchased one of these products to explain the situation and issue a refund.
'We will continue to leverage and improve our tools and technology to ensure only safe and compliant car seats are available worldwide.'
If you are looking to buy a baby or child car seat, follow these tips:
We crash test every baby, toddler and child car seat we review to reveal which ones give the best protection in a crash, and which you should avoid.
Our experts have specially designed the crash tests, making them more demanding than the legal minimum standard requires. We feel this more accurately reflects what could happen in a real crash.
The Panorama programme Amazon: What They Know About Us will be broadcast on BBC One at 20:30 GMT.