Which? searched Amazon for 14 different technology products, including cameras, headphones and smart-watches, "and found that some appear to be far more heavily targeted by potentially fake reviews and "unknown" brands - companies our tech experts had never heard of". "We even found instances of positive reviews for entirely different products appearing on a listing".
More perniciously researchers found evidence that such content had the potential to unfairly propel listings for little-known brands further up search rankings.
A study by the consumer group Which? found Amazon was "flooded" by fake reviews.
"It took just a couple of hours to uncover more than 10,000 reviews from unverified purchasers on just 24 pairs of headphones - an easy-to-find red flag that highlights the scale of Amazon's problem with fake reviews", the group wrote in a post detailing the findings of its investigation. "Even one inauthentic review is one too many".
Of 12,000 reviews for these, the majority (87%) were from unverified purchases. Also on the first, page, 71% had a flawless 5-star review score and 87% of the products were unverified, or not confirmed as an Amazon purchase.
Which? found similar results when searching for smartwatches, with unverified reviews making up 99% of reviews for the top four products.
The pattern was repeated with action cameras, fitness trackers and wireless security cameras - with more than nine in ten of the top-rated products in each category made by unknown brands and boosted by a deluge of dubious reviews.
It said it invested "significant resources" to protect its review system "because we know customers value the insights and experiences shared by fellow shoppers".
The tech giant's spokesperson continued: "We use a combination of teams of investigators and automated technology to prevent and detect inauthentic reviews at scale, and to take action against the bad actors behind the abuse".
It confirmed that it uses machine learning tech to analyse reviews 24/7 as well as working with social media sites to block fake reviews at the source.
Neither Which? nor the Guardian were able to contact any of the brands cited in the report, or to identify the source of the suspicious reviews. Which? said these were not as valuable as the independent and long-running product tests it carries out.