Enlarge / Cardboard boxes made to resemble Amazon packages during a protest outside the home of Amazon Chief Executive Officer Jeff Bezos in New York on Wednesday, Dec. 2, 2020. (credit: Getty Images / Bloomberg Collection )

Posing as an Amazon seller, a UK consumer group dug into the shady marketplace where fake reviews are sold in bulk by companies promising sellers a quick rise to the top of Amazon's charts.

"In December 2020, we signed up to 10 sites offering review manipulation services, including free or discounted products in exchange for reviews, or sales campaigns for sellers to boost their positive reviews," according to the report published yesterday on Which? , a website run by the Consumers' Association, a UK-based charity that does product research and advocacy on behalf of consumers. The consumer group said it found an army of "702,000 product reviewers across just five businesses" and "one site selling contact and social media details for Amazon reviewers."

One review seller is a German company called AMZTigers. "Amazon prohibits sellers from paying third parties in exchange for reviews, and says that it suspends, bans and takes actions against those who violate these policies. But this is exactly the sort of service AMZTigers offers," the report said. "We posed as an Amazon seller and signed up to find out more. After a short registration, we were assigned an account manager who arranged a call to discuss what we were looking for, including whether we already had stock to sell."