Google and Facebook face punishing fines unless they remove terrorist propaganda within a two-hour limit.

Theresa May will use a summit in New York tonight to warn the technology giants and their rivals that her patience is running out over their failure to clamp down on jihadi groups.

She will say they have only a month to make progress. If they don’t, the Government will legislate to make them liable for extremist content on their sites. Delay in removing the material would trigger fines.

Prime Minister Theresa May (pictured) will use a summit in New York to warn Google and Facebook they need to do more to combat the spread of terrorism online

The Daily Mail yesterday revealed how easy it is to find terrorist content online – including guides on how to carry out truck, knife and bomb attacks.

Many of the links are still live despite a string of atrocities on British soil.

The Prime Minister will call on the internet giants to develop technology to block the material before it can go online.

Any that slips through the net would have to be removed within two hours ‘at most’.

Amid mounting international concern at foot-dragging by the technology firms, Mrs May’s demands will be backed by French president Emmanuel Macron and Italian prime minister Paolo Gentiloni.

Mrs May said: ‘We need a fundamental shift in the scale and nature of our response – both from industry and governments – if we are to match the evolving nature of terrorists’ use of the internet.’

Mrs May will say the web giants have only a month to make progress. If they don’t, the Government will legislate to make them liable for extremist content on their sites

Downing Street said she would warn firms of fines if they failed to cooperate.

The PM’s official spokesman said: ‘We want to do this in a voluntary way but we are prepared to look at the issue of legal liability if we do not make good progress.’

Making the internet giants legally liable for the extremist content on their sites could leave them open to huge fines.

The threat is designed to put pressure on the firms to use their technological prowess to counter sophisticated efforts by Islamic State and other terror groups to radicalise impressionable youngsters and spread DIY terror manuals online.

The PM will say tonight: ‘Terrorist groups are aware that links to their propaganda are being removed more quickly, and are placing a greater emphasis on disseminating content at speed in order to stay ahead.

‘Industry needs to go further and faster in automating the detection and removal of terrorist content online, and developing technological solutions that prevent it being uploaded in the first place.’

Google could face huge fines unless they do more to clamp down on jihadi groups

The two-hour target is seen in government as a first step. Industry will then be expected to cut this to one hour and, ultimately, use sophisticated software and artificial intelligence systems to prevent such material appearing at all.

Islamic State put up 27,000 new videos in the first five months of this year aimed at radicalising youngsters and guiding them on how to launch attacks.

The security services say supporters act to spread the material like wildfire – two thirds of the dissemination takes place within two hours.

A Government source said: ‘These companies have some of the best brains in the world. They should really be focusing that on what matters, which is stopping the spread of terrorism and violence.’

The Mail has led the way in exposing the failure of technology firms to take their responsibilities seriously.

In the wake of the Westminster and London Bridge attacks, this newspaper revealed the ease with which manuals showing how to conduct attacks with cars and knives could be found online.

Last week, the Mail revealed that a seven-year-old guide on how to make a bucket bomb like the one used in the Parsons Green attack was available online. It was still located via web searches last night, as were step-by-step guides to making car bombs, explosives and detonators – 24 hours after the Mail flagged the links to Google.

A jihadi terror manual on bomb-building was still circulating on Twitter – including on one tweet that the Mail reported to the site nearly three months ago.

The message links to a terrorism handbook that gives would-be jihadists instructions on how to make nail bombs and turn household items into ‘tools of war’.

In the wake of the Parsons Green terror attack (pictured) in London last week, terrorist material was still easily available online

Technology firms insist they are now taking the issue seriously.

Twitter revealed that almost a million accounts have been suspended in the past two years for promoting terrorism and Google said it was ‘making significant progress’.

But ministers believe the firms are still dragging their feet.

Today’s summit will be attended by Google, Facebook, Twitter, Microsoft and a range of smaller technology firms. Major advertisers, who are queasy about the bad publicity the issue has attracted, will also be in attendance.

Ministers believe that commercial pressure, and the publicity brought by campaigns such as that in the Mail, have helped bring the firms to the table.

In her speech to the UN General Assembly in New York today, the PM will urge world leaders to do more to crack down on terrorism. Mrs May, who has had to deal with five terror attacks in the UK this year, will praise the resilient response of the public in London and Manchester.

But she will add: ‘Defiance alone is not enough.

‘In the last decade hundreds of thousands have been killed by terrorists across the world. This is a truly global tragedy that is increasingly touching the lives of us all. As Prime Minister, I have visited too many hospitals and seen too many innocent people murdered in my country.

‘When I think of the hundreds of thousands of victims of terrorism in countries across the world, I think of their friends, their families, their communities, devastated by this evil.

‘And I say enough is enough.’