Facebook groups offering fake reviews on the likes of Amazon, Google and Trustpilot are persistent despite regulators’ demands that tech platforms do more to tackle the issue, according to an investigation by a consumer group.

Groups on the social network with thousands of members offer free products in exchange for reviews, said the consumer group Which?, despite past interventions by UK regulators.

Researchers found 14 Facebook groups trading in reviews for Amazon, Google and Trustpilot. Together they shared more than 62,000 members between them.

Fake reviews have become one of the most persistent scourges of online retailers, and the UK government is expected to make the practice illegal in the forthcoming digital markets, competition and consumer bill. The bill would make it illegal to pay someone to write a fake review or to host a review without taking steps to check it is real.

The UK’s Competition and Markets Authority told Facebook to clamp down on fake reviews in 2020 and again in 2021, when the social network removed more than 16,000 groups. Which? estimates that the groups it has reported to Facebook since 2018 have had more than 1 million members in total.

Rocio Concha, the consumer group’s director of policy and advocacy, said: “An industry dedicated to fake review trading continues to thrive on Facebook, leaving consumers exposed to misleading information on some of the world’s biggest review and shopping platforms.”

She said the “strong enforcement and tough penalties for platforms that fail in their legal responsibilities” promised by the UK government was “sorely needed to tackle fake reviews”.

A spokesperson for Meta, Facebook’s parent company, said: “Fraudulent and deceptive activity is not allowed on our platforms, including offering or trading fake reviews. We’ve removed the groups shared with us for violating our policies. While no enforcement is perfect, we continue to invest in new technologies and methods to protect our users from this kind of content.”

Six of the newly identified groups offered free products in exchange for Amazon reviews. One group identified by Which?, “Amazon Reviewer – Test Products”, counted 15,000 members.

On a group sharing that name, the Guardian found posts appearing to ask for UK, US and French buyers of products including a garlic crusher, wireless headphones, and designer-imitation handbags. Comments on the groups and the research by Which? suggested that users would buy the products, and then receive a refund once they had given a five-star review.

Spokespeople for Amazon and Trustpilot said they actively monitored Facebook groups and reported incentivised reviews, and that they employed teams of investigators. “By taking this action against fraudsters, we are going after the source of the problem and shutting down these fake review businesses,” the Amazon spokesperson said.

The Trustpilot spokesperson said: “We closely monitor Facebook groups claiming to sell fake reviews on Trustpilot, and we take strong and robust action to combat the practice.”

A Google spokesperson said: “Our policies clearly state reviews must be based on real experiences, and when we find policy violations, we take swift action ranging from content removal to account suspension and even litigation.”