Which? found that 78,000 reviews for popular tech products have been removed in the last three years. However, it found the vast majority of 12,000 reviews displayed on the first page of certain products were from unverified purchasers - those who Amazon cannot know if they bought the product - or had suspiciously high five-star ratings, two of the key red flags for fake reviews.
It said that high numbers of unverified, positive product reviews could be an indication that a product’s overall rating is being manipulated by fake reviews.
Meanwhile, the consumer watchdog said it had exposed Amazon “review factory” Facebook groups, which encourage users of the social network to post positive reviews in return for payment of other incentives and further erode trust in the reliability of Amazon reviews.
According to data from online review checker ReviewMeta, in the first quarter of 2018, six per cent of the reviews on Amazon were unverified, Which? said - but for the same period in 2019, this had risen to 31 per cent. Meanwhile, last month, the number of unverified reviews on Amazon rose by nearly 300 per cent compared to the previous month, with average star ratings of unverified reviews at 4.95 out of five.
Which? also said it found tens of thousands of potentially fake reviews on just a couple of dozen products, which it said suggests that far more needs to be done to truly address the problem.
Natalie Hitchins, Which? head of home products and services, said: “Our research shows that while thousands of potentially fake reviews are being removed from Amazon each month, this isn’t nearly enough to address a real problem for online shoppers that seems to be getting worse, not better.
“To avoid being tricked into buying a product that you might otherwise have avoided, watch out for fake reviews and search for independent and trusted sources when looking to make a purchase.”
Amazon said that it estimates that more than 90 per cent of inauthentic reviews are computer generated. The company said it uses machine learning technology to analyse all incoming and existing reviews 24/7 and block or remove inauthentic reviews.
Many of the products or suspect reviews uncovered during the Which? investigation have been removed.
A spokesman for Amazon said: “The approach taken by Which? is flawed and its findings—based on research from an organisation that admits it can’t say whether any review is ‘fake’ and does not know how many reviews have been removed from Amazon—are inaccurate.
“Amazon invests significant resources to protect the integrity of reviews in our store because we know customers value the insights and experiences shared by fellow shoppers. We have clear participation guidelines for both reviewers and selling partners and we suspend, ban, and take legal action on those who violate our policies.”
A spokesman for Facebook said: “We don’t allow people on Facebook to facilitate or encourage the trade of fake user reviews. The groups brought to our attention have now been removed for violating our policies.
“We urge people to continue to use our reporting tools to flag content they think break our rules so that we can investigate and take swift action.”
The Competition and Markets Authority estimates that £23 billion a year of UK consumer spending is potentially influenced by online reviews and has warned that writing or commissioning fake reviews could lead to civil or criminal action.