The Competition and Markets Authority has found “troubling evidence” of a thriving marketplace for fake and misleading online reviews, it has revealed.

The regulator said that it had found over 100 listing on eBay selling fake review and 26 Facebook group with users offering a similar service.

The CMA said it is estimated that three quarters of UK consumers look at review before buying a product, a fact which could lead to billions of pounds spent on products with illegal, paid-for reviews.

The CMA said it was not alleging that Facebook or eBay were intientally allowing the content to appear, but that noth have been concatced and have indictaed they will cooperate.

Facebook took down most of the 26 groups identified, it said.

“Fake reviews mean that people might make the wrong choice and end up with a product or service that’s not right for them,” explained Andrea Coscelli, CMA Chief Executive.

“They’re also unfair to businesses who do the right thing. We want Facebook and eBay to conduct an urgent review of their sites to prevent fake and misleading online reviews from being bought and sold.”

The announcement will form the first phase of a wider programme of CMA work aimed at tackling fake and misleading reviews.

“We have zero tolerance for fake or misleading reviews,” an eBay spokesperson told Reuters.

“Listings such as these are strictly against our policy on illegal activity and we will act where our rules are broken.”