BBC Panorama discovered these products as part of a broader plan.
The US company has repeatedly faced complaints about listing such seats.
A case dating back to 2013 led to a trade standards investigation that confirmed that if an example of a 30 mph [48 km / h] crash occurred, it would be torn apart.
Recently, which one? The magazine found some examples of fabric-based seats on Amazon that lack the required safety labels on the seats 2019. Other stores, including eBay, were also found to be selling the items at the time.
No security label
The latest case involves four obscure brands.
Panorama tried to contact the brands involved. It received only one response, saying that it was not the manufacturer.
The program purchased three suspicious seats. Their designs are similar to those involved in the 2013 case and they lack safety labels.
The head of Amazon UK said the company has taken proactive measures to ensure the safety of the products it sells.
"Automatic algorithms [surveys] exceed 5 billion product pages per day and we monitor tens of millions of customer reviews," Doug Gurr said.
The company added in a follow-up statement: "Security is very important to us and we regret that these products are available from third-party sellers who use our store.
"After thorough investigation, we found the problem and are removing these products, and we will also contact each customer who purchased one of these products to explain the situation and refund.
"We will continue to leverage and improve our tools and technologies to ensure that only safe and compliant car seats are available worldwide."
Currently, operators of online markets, including the Amazon store, can be exempted from liability if they do not know the illegal content sold on their platform.
But which one? This has been promoted as part of the upcoming Online Harm Act.
"The voluntary nature of current market checks has failed to recognize their role as the main interface for consumers' technical and commercial capabilities, enabling them to hold suppliers accountable for consumer safety." It was released in November.
"In drafting this legislation, clearer government guidance is needed."
Amazon has sent emails to consumers who bought their seats.
They said: "The product you received from a third-party seller may not meet the applicable child restraint standards.
"If you still have this product, stop using it immediately, cut off the belt to make it unusable, and then discard the product."
Amazon: What they know about us will air on BBC One at 20:30 GMT