UK Home Secretary Amber Rudd has announced a tool that purports to detect and block jihadist content online, and tech companies may end up being legally required to use it.

London-based firm ASI Data Science was handed £600,000 by government to develop the unnamed algorithm, which uses machine learning to analyse Daesh propaganda videos.

According to the Home Office, tests have shown the tool automatically detects 94 per cent of Daesh propaganda with 99.995 per cent accuracy.

The department claimed the algorithm has an "extremely high degree of accuracy", with only 50 out of a million randomly selected videos requiring additional human review.

Many companies with huge online platforms, such as Google and Facebook, already claimed to have developed technology to root out extremist content. But the government said its algorithm could be used by smaller platforms that do not have the same level of resources to develop technology.

Rudd told the Beeb the government would not rule out taking legislative action "if we need to do it".

In a statement she said: "The purpose of these videos is to incite violence in our communities, recruit people to their cause, and attempt to spread fear in our society. We know that automatic technology like this, can heavily disrupt the terrorists' actions, as well as prevent people from ever being exposed to these horrific images."

Rudd is currently touring Silicon Valley for a series of meetings with the main communication service providers to discuss tackling terrorist content online.

However, she has been subject to some ridicule by the sector: previously speaking about preventing the uploading of objectionable content, she said the government needs to get people who "understand the necessary hashtags" talking.

She has also admitted that she doesn't know how encryption works, and has criticised "patronising" techies that "sneer" at politicians.

During her visit to the US west coast, Rudd will discuss what companies are doing to develop methods that identify Daesh propaganda, and support smaller companies, such as Vimeo, Telegra.ph and pCloud to remove terrorist content from their platforms.

As part of her two-day visit to San Francisco, she will meet Secretary of Homeland Security Kirstjen Nielsen to discuss how the UK and US can work together to tackle terrorist content online, and the pair will appear at a Digital Forum event later today.

Rudd will also meet the Global Internet Forum to Counter Terrorism, which was launched last year following a roundtable convened at the Home Office in the aftermath of the Westminster Bridge attack. ®