The prime minister is to call on investors to boycott social media platforms that do not delete and censor perceived “extremist” views.

Speaking at the Davos World Economic Forum, Theresa May will argue that not enough is being done to fight terrorism and paedophiles online.

However, right-wing opinions are already frequently censored on social media and other schemes championed by Mrs. May, such as the Prevent count-terror programme, have been used to target critics of Islam and members of UKIP.

“Technology companies still need to go further in stepping up to their responsibilities for dealing with harmful and illegal online activity,” the prime minister will say according to advance extracts of her speech.

“These companies simply cannot stand by while their platforms are used to facilitate child abuse, modern slavery, or the spreading of terrorist and extremist content.”

Mrs. May will say that some progress has been made on the automatic removal of unfavourable content, but will call on investors exert further financial pressure to force certain views offline.

Appearing to directly address business leaders, she will add: “Investors can play a vital role by considering the social impact of the companies they are investing in. They can use their influence to ensure these issues are taken seriously.”

Tech companies need to take their responsibilities to society seriously. That’s why today at #Davos18, in front of the world’s leading business men and women, I will set out how together we can shape the standards, norms and rules of how we behave in the digital world. #WEF18 pic.twitter.com/PMgXWVTNvL — Theresa May (@theresa_may) January 25, 2018

Data published last week showed social media companies have accelerated the censorship of “hate speech” on their platforms following European Union threats of a crackdown on some opinions.

“Hate speech” is widely defined as any view or comment that is “perceived” as hurtful of “offensive” by the “victim”. UK police include “dislike” and “unfriendliness” in their definition.

The German parliament passed laws last year threatening social media firms with fines of up to €50 million if they do not remove content deemed criminal because it could be perceived as defamatory or “hate speech” quickly enough.

The law has led to satirical posts being removed and a leader of the right-wing populist AfD party being censored for criticising police policy and Islam.

However, the German population is, in general, more supportive of censorship than Brits, with a recent Pew Research Center poll finding seven in 10 people back the government banning statements that could be offensive to minorities.

In the UK, just 38 per cent of people think this way.

The government’s Prevent programme, championed by Mrs. May as home secretary, is supposed to target potential violent terrorists.

However, a large and increasing proportion of referrals are from the so-called “far right” and UKIP-supporting school children and opponents of the Islamic face veil have all been approached by police connected with the scheme.