Google is failing to do enough to combat fake reviews within its business listings, and must be held to account by a UK watchdog, according to Which?
The consumer group set up a fake company and bought bogus five-star reviews as part of an investigation.
In doing so, it was able to tie its sham "customers" to dozens of other highly-rated British firms, including a dentist and a stockbroker.
Google says it has "significantly" invested in tech to tackle the issue.
But it and other review sites are in the sightlines of the Competition and Markets Authority, which began examining the sector last year. It has threatened enforcement action against platforms which have fallen short of their responsibilities.
Previous research from Which? suggests that nearly half of people who check online reviews of local businesses read them on Google.
How did they find them?
Which? conducted its research by essentially setting up a "sting" operation to catch unscrupulous operators in the act.
It created a fake business listing which it called "five-star reviews", and searched online for companies advertising paid-for Google reviews. It then spent $150 (£108) on their services.
Which? told each company it wanted five-star reviews only, and between three and five of them a day - and the consumer group's researchers wrote the reviews themselves, "praising how good the made-up business and its fake owner Catherine are".
The fake reviews appeared over the following week, a few at a time.
But in investigating the "reviewers" behind them, the Which? team found, among others:
- 15 reviewers who had rated both an Edinburgh search engine optimisation business and a London psychic as five stars, which it called "an unlikely coincidence"
- A stockbroker in Canary Wharf who, having had several bad reviews in mid-2020, received 30 five-star ones "in quick succession" a few months later
- A reviewer who claimed to have lived in Surrey for years while praising a local car company, and a Glasgow electric gate firm 412 miles (663 km) away for work on his home
- The same reviewer also praised a dentist in Manchester, a paving firm in Bournemouth, and a Cambridgeshire locksmith, who allegedly saved his toddler from a locked car
Which? said it linked some 45 businesses scattered across the country to three suspicious "reviewers". That suggested they had each paid the same review seller to post their reviews, it said.
Why does it matter?
Which? said that some fake reviews could have serious real-world consequences. For example, one claimed that a Liverpool solicitor had helped them recover tens of thousands of pounds. If false, it could scam people in a vulnerable financial position, the group argued.
In another, the positive reviews outweighed several presumably genuine negative reviews which warned customers away from allegedly unscrupulous or "scam" companies.
"Businesses exploiting flaws in Google's review system to rise up the ranks are putting honest businesses on the back foot and leaving consumers at risk of being misled," said Natalie Hitchins from Which?.
It called on regulators and Google to take action.
When it presented Google with the findings, the fake sting company was immediately deleted, Which? said.
Google said that its policies ban fake reviews, and that it monitors the system for fraud around the clock, "using a combination of people and technology".
"When we find scammers trying to mislead people, we take swift action ranging from content removal to account suspension and even litigation," the company said.
Which? did find that one of the fake reviews was removed by Google during the course of its investigation - but the firm it bought from said it would "slow down" the rate of fake review posting so future ones would "stick".
The consumer group also offered the review-selling companies which it had researched the opportunity to say something.
Only two replied: one to argue that its services help new businesses to get started and that it was not breaking any Google terms and conditions; and another to deny that it had ever sold any fake reviews and that Which? was mistaken.