New tool for preventing damaging adverts is branded "completely useless"

The ad claimed to have been paid for by Cambridge Analytica which shut earlier this year amid the Facebook scandal. [Photo: PA]

An advert purporting to be paid for by now defunct company Cambridge Analytica was posted to Facebook containing using materials from pro-Brexit group BeLeave. Except neither was involved.

Facebook recently launched a new tool that allows users to see details about adverts for political and nationally important topics. The goal was to help stop the spread of fake news and hatred, but it turns out the system barely functions at all.

According to the BBC the advert was placed by news site Business Insider for a story about Facebook's transparency tools.

The site booked the ad using the name Insider Research Group - clearly a reference to Business Insider - but marked as "paid for by Cambridge Analytica".

Facebook allowed the ad to run although the social media company pulled it at some point. Business Insider spent less than £100 and reached between 1,000 and 5,000 Facebook users.

Facebook's own rules state that any company running ads on political or nationally sensitive issues needs to first be verified. The process for this involves sending photo ID to the company.

The process for verification claims that companies placing ads will need their business address to be verified via post. Political ads for the UK also need to be placed within the UK.

But not picking up on the use of the Cambridge Analytica name, the culprit in one of Facebook's biggest data theft scandals, raises serious questions about the suitability of the new tools for their intended task.

Guardian journalist Carole Cadwalladr spotted the ad and posted it on Twitter.