Amazon's murky world of one-star reviews
Amazon's marketplace is being abused by independent sellers using one-star reviews to harm rivals, the BBC has been told.
Newsnight spoke to a number of those affected who believe their sales have suffered as a consequence.
A consumer rights champion now wants a UK watchdog to investigate further, as part of a probe into fake reviews that is already under way.
Amazon claims to be "relentless" in tackling review manipulation.
Even so, some of those targeted believe it cannot eradicate the problem.
Third-party vendors have sold more physical goods on Amazon's site than the US tech giant itself every year since 2015, according to its own figures.
The Competition and Markets Authority believes that £23bn of online shopping in the UK is influenced by reviews.
Perhaps it's not surprising then that some online retailers are playing dirty.
"The sad thing is that you could have 50 positive reviews, like five-star reviews - but if you've got one or two one-star reviews, then it's going to be very difficult to compete," Janson Smith, a third-party Amazon seller, told the BBC.
I asked if he would want an additional 20 five-star reviews, if they were accompanied by a single one-star rating.
"No" he replied.
Fake positive reviews on the net are a well-known problem,.
Previous reports have exposed "factories" of bogus reviewers involved in posting five-star write-ups in exchange for freebies.
Only last week, the Financial Times reported some of Amazon's top-ranked UK reviewers appeared to be engaged in such activity. Amazon removed 20,000 fake positive posts over the weekend.
But some sellers now believe it's fake one-star feedback that is the new front of review manipulation.
Ella Keyes had a flourishing business selling post-pregnancy products on Amazon.
She says she had about 60 reviews, almost all of them positive. She was making roughly £3,000 a month.
Then something strange happened - she got a flurry of one-star reviews.
image captionMs Keyes used to sell products to help women deal with post-pregnancy recovery
"Initially when the first couple came it didn't make too much of an impact because I had enough positive reviews to sort of offset it", she recalled.
"But when more and more started coming in, I noticed that sales just dropped off a cliff.
"Anything below [an average of] 4.5 and you're kind of done."
Ella believes some of these negative reviews were fake, and the stress began to get to her.
After a few months she abandoned the venture.
Janson Smith says something similar happened to him, but he decided not to go down without a fight.
He cross-referenced the negative reviews he had received with the orders, and came to realise almost all had come from suspicious accounts. He managed to get Amazon to remove them.
He has since set up an online consultancy to help other Amazon sellers facing this and other predicaments.
image captionJanson Smith advises other sellers on how to avoid potential pitfalls on Amazon
"I think that now sellers have realised it's very hard to fake getting four-star or five-star reviews," he explained.
"So they're like 'hang on let's now bring the competition down so that our score is relatively higher'."
do you use Amazon?
Indeed, there are a lot of fake reviews and you can't be 100% sure about the seller. I don't remember who shared the service with me anymore https://www.inc.com/profile/PissedConsumer but I will say that I now carefully check the reviews before making a purchase on the Internet. You can read more about this company in more detail. Customer complaints should be heard and consumer protection is more important than ever in our time.