A survey by the consumer champion found that a third (34%) of victims who reported an advert that led to a scam on Google said the advert was not taken down by the search engine.

Meanwhile a quarter (26%) of victims who reported an advert on Facebook that resulted in them being scammed said the advert was not removed by the social media site.

Which? believes that the significant flaws with the current reactive approaches taken to tackling online scams makes a clear case for online platforms to be given legal responsibility for preventing fake and fraudulent adverts from appearing on their sites.

Which? is calling for the government to take the opportunity to include content that leads to online scams in the scope of its proposed Online Safety Bill.

Of those who said they had fallen victim to a scam as a result of an advert on a search engine or social media, a quarter (27%) said they’d fallen for a fraudulent advert they saw on Facebook, one in five (19%) had been targeted via Google adverts, while 3% said they’d been tricked by an advert on Twitter.

The survey also highlighted low levels of engagement with the scam reporting processes on online platforms. Two in five (43%) scam victims conned by an advert they saw online said they did not report the scam to the platform hosting it.

The most common reason for not reporting adverts that caused a scam to Facebook was that victims didn’t think the platform would do anything about it or take it down.

For Google, the main reason for not reporting the scam ad was that the victim didn’t know how to do so – this applied to a third (32%) of victims. This backs up the experience of Which?’s researchers who similarly found it was not immediately clear how to report fraudulent content to Google, and when they did it involved navigating five complex pages of information.

Another issue identified by victims that Which? has spoken to is that even if fake and fraudulent adverts are successfully taken down they often pop up again under different names.

Google and Facebook make significant profits from adverts, including ones that lead to scams. Which? says these tech giants have some of the most sophisticated technology in the world but they fail to use it to prevent scammers posting fake and fraudulent content on the platforms.

Adam French, consumer rights expert at Which?, said: “Our latest research has exposed significant flaws with the reactive approach taken by tech giants including Google and Facebook in response to the reporting of fraudulent content – leaving victims worryingly exposed to scams.

“Which? has launched a free scam alert service to help consumers familiarise themselves with the latest tactics used by fraudsters, but there is no doubt that tech giants, regulators and the government need to go to greater lengths to prevent scams from flourishing.

“Online platforms must be given a legal responsibility to identify, remove and prevent fake and fraudulent content on their sites. The case for including scams in the Online Safety Bill is overwhelming and the government needs to act now.”