Facebook and Google lack effective controls to prevent fraudsters from posting scam adverts, according to a Which? investigation.

It is possible for bogus adverts devised by bad actors to appear within a matter of hours, the consumer group has warned, after carrying out a test of its own.

While both tech giants have improved ad transparency and toughened rules in recent years, Which? said it is still possible for false advertising to slip through the net.

Researchers created two linked fake companies – a water brand named Remedii and Natural Hydration, an online service offering pseudo health and hydration advice – to see how easy it would be.

No fake products were sold during the experiment.

They found that Google did review the adverts submitted, but failed to verify whether the business was real and did not ask for ID.

The Government should widen its definition of 'online harms' to include fake adverts and content, which would mean future regulation would require more action from tech companies to tackle false advertising

In under an hour, the adverts were approved by the search engine firm for both dummy businesses, gaining almost 100,000 impressions over the space of a month.

The fake advert for Natural Hydration was displayed above the official NHS Scotland pages when users searched for “hydration advice”.

Meanwhile, using a personal Facebook account, Which? created a business page on the social network for Natural Hydration and produced a range of posts with pseudo health advice to promote it.

A paid promotion of the page gained some 500 likes in the space of a week.

Facebook responded to the investigation saying the page set up by Which? does not violate its community standards and is not currently selling products.

“We remove harmful misinformation that could contribute to physical harm, such as false health claims, and have strict policies against deceptive advertising and scams,” it said.

Google has already set out plans to introduce new rules in the UK from early 2021 which will require all advertisers to complete an identity verification programme.

“Protecting consumers and credible businesses who rely on our services is our top priority, and we take this responsibility seriously. We have strict advertising policies in place to protect consumers and prohibit ads that intentionally mislead users or fail to deliver on the promoted product or service,” a spokesman said.

“When we become aware of ads that violate our policies, we take action.

“We are also constantly evaluating our policies and enforcement systems to continue to improve and have recently introduced a new programme to verify each advertiser’s identity in order for them to serve ads on our platforms.”

It comes as the UK’s competition watchdog called for new fines and the threat of break-ups for tech giants with dominant positions in the advertising space.

According to the Competition and Markets Authority (CMA), UK expenditure on digital advertising was around £14 billion in 2019, with 80% of it going to Facebook and Google.

It wants a new pro-competition regulatory regime in place to reduce their power, backed by a code of conduct to ensure such platforms do not engage in exploitative or exclusionary practices.

“Fraudulent activity is rife on social media and search engines and our investigation has exposed that a lack of controls on Facebook and Google has made it worryingly easy for fraudsters to create adverts promoting scams or fake products and services,” said Harry Rose, Which? magazine editor.

“Tech giants earn billions from advertising and should be putting more resources into preventing fraudsters from abusing their platforms, so consumers can trust that the adverts they see are legitimate.

“The Government should widen its definition of ‘online harms’ to include fake adverts and content, which would mean future regulation would require more action from tech companies to tackle false advertising.”