Amazon is promoting poor-quality products with an “Amazon’s Choice” badge as cunning sellers manipulate the algorithmic recommendation system behind the label, according to research from the consumer rights group Which?.

Many of the most popular items sold on Amazon.co.uk are labelled Amazon’s Choice, a thin blue badge that renders a product more visible on the search results page.

Despite the name, Amazon does not actively select the products it declares its choice: the company instead automatically bestows the commendation on products that match an undisclosed set of criteria including good reviews, low price and fast shipping.

That means that if unscrupulous sellers are able to generate good reviews for mediocre, unsuitable or dangerous products, they can succeed in getting their items the coveted label, Which? said.

“Amazon risks betraying the trust millions of customers place in the Amazon’s Choice badge by allowing its endorsement to be all too easily gamed,” said Which?’s Natalie Hitchins. “Amazon must ensure its customers aren’t being misled about the products it is recommending to them – or reconsider whether it should continue with the endorsement in its current form.”

Which? highlighted a number of examples of manipulation that seemed to lead to unwarranted selection as an Amazon’s Choice product, including a car dashcam that had at least 24 written reviews mentioning the offer of a free SD card in exchange for a positive review, and a pair of wireless headphones that had close to 2,000 reviews thanks to the use of a feature called product merging – the majority of the positive reviews were about unrelated products including acne cream and razor blades.

An Amazon spokesperson said: “When browsing our store, customers may see a product highlighted as Amazon’s Choice for their specific shopping request. Amazon’s Choice highlights highly rated, well-priced products that are available to ship immediately. Amazon’s Choice is our choice for a product we think customers may like, and customers can always shop for any brand or product that they want to purchase.

“We don’t tolerate Amazon policy violations such as review abuse, incentivised reviews, counterfeits or unsafe products. When deciding to badge a product as Amazon’s Choice, we proactively incorporate a number of factors that are designed to protect customers from those policy violations. When we identify a product that may not meet our high bar for products we highlight for customers, we remove the badge.”

Amazon added that it has removed the Amazon Choice branding from the items Which? complained about.

Which? said Amazon shoppers widely believe the Amazon Choice label confers a more direct recommendation than it actually does. According to its polling, 44% of Amazon’s customers think it means a product has been quality-checked by Amazon, and 35% think it means it has been checked for safety.

Amazon has faced increasing criticism for the lack of quality control on its site. The company earns an increasing amount of its revenue through “marketplace” sales, for which it provides its platform and offers minimal oversight, and it has altered its site in a way that blurs the distinction between those sales and products bought directly from Amazon itself.

A Guardian investigation in 2018 found that the site was awash with counterfeit goods as a result, with fake streetwear, electronics and makeup on sale as the genuine items.

A year later, the Wall Street Journal found “thousands of banned, unsafe or mislabelled products” being sold on the site by third-party sellers, ranging from sleeping mats that had been banned over fears they would suffocate infants to motorcycle helmets falsely listed as government-certified. “Dozens of products the Journal identified as dangerous or mislabeled had the Amazon’s Choice designation,” the newspaper said.

• This article was amended on 6 February 2020 to note that Amazon says that it has removed the Amazon Choice branding from the items Which? complained about.