Amber Rudd in warning over terrorist activity on internet giants' platforms
The Home Secretary will warn internet giants that terrorists are misusing their platforms when she visits Silicon Valley on Tuesday.
Amber Rudd will challenge the likes of Facebook, Twitter, Microsoft and Google to do more to remove extremist content.
Major technology organisations have repeatedly faced calls to step up efforts to detect and take down terror-related videos and web pages, and pressure for fresh action has intensified after Britain was hit by a flurry of attacks.
The companies have launched the Global Internet Forum to Counter Terrorism to seek out technical solutions and draw up "counter-narratives".
Speaking at the forum's inaugural meeting in San Francisco, Ms Rudd will acknowledge the work firms have already done.
She will also highlight the work of a UK police unit which has secured the removal of 280,000 pieces of terrorist content and the closure of millions of accounts since 2010.
But the Home Secretary will emphasise that more needs to be done and the threat cannot be downplayed.
"Terrorists and extremists have sought to misuse your platforms to spread their hateful messages," Ms Rudd is expected to say.
"This Forum is a crucial way to start turning the tide.
"The responsibility for tackling this threat at every level lies with both governments and with industry.
"We have a shared interest: we want to protect our citizens and keep the free and open internet we all love. Today's meeting of the Forum is the next step towards achieving these goals."
Ms Rudd is visiting Silicon Valley to hold a number of meetings with the main communication service providers.
Earlier this year, a committee of MPs accused social media firms of a "shameful" failure to tackle online terrorist propaganda and hate speech.
In June Metropolitan Police Assistant Commissioner Mark Rowley, the country's most senior counter-terror officer, urged internet-based companies to "show more responsibility".
Writing in the Times, he warned: "It is too easy for the angry, violent or vulnerable to access extremist views, learn about attack methodologies, conspire on encrypted applications and then acquire equipment to kill, all online."
Britain and France are looking at plans that could see technology firms face fines if their efforts to tackle terrorist material are not up to scratch.
The proposals - unveiled by Theresa May and French president Emmanuel Macron in June - include exploring the possibility of creating a new legal liability for companies if they fail to remove unacceptable content.
Ms Rudd will also raise the issue of encryption during the talks.
Scrutiny has focused on so-called end-to-end encryption, which is built into messaging services such as WhatsApp and means that messages are encoded in such a way that only the sending and receiving devices can read them.
Ministers want to clamp down on online "safe spaces" where terrorists and other serious criminals can communicate without detection.
Last month Metropolitan Police Commissioner Cressida Dick warned that encryption was frustrating investigations on a daily basis.
The Home Office said Ms Rudd will press companies to work with the UK to find "practical solutions" to the challenges faced in relation to end-to-end encryption so law enforcement agencies can lawfully access data needed for public protection.
Ms Rudd will reiterate the Government's position that it supports strong encryption, and that there are no plans to ban end-to-end encryption, but she will argue that the ability to stop terrorist attacks is being limited by the inability to gain access to encrypted data in specific and targeted instances.