Global internet companies have become ‘the command and control networks of choice’ for terrorists, claims the new head of Britain’s electronic spying agency.

GCHQ director Robert Hannigan insisted some were ‘in denial’ about the way fanatics misuse their services.

He cited how Islamic State (IS) has exploited social media for recruitment and propaganda – using the likes of Twitter, WhatsApp and YouTube to promote beheadings. The terror group and its followers have also sent up to 40,000 tweets a day.

An aerial view of Government Communications Headquarters in Benhall, in the suburbs of Cheltenham, Gloucestershire: The agency's new chief says internet firms need to open up even more to state spies

Mr Hannigan called on the likes of Google, Facebook, Twitter and Microsoft to give greater co-operation to GCHQ and sister agencies MI5 and MI6.

He also said there was ‘no doubt’ young foreign fighters had benefited from the treasure trove of intelligence secrets leaked by fugitive CIA worker Edward Snowden.

‘GCHQ and its sister agencies… cannot tackle these challenges without greater support from the private sector, including the largest US technology companies which dominate the web,’ he said.

‘I understand why they have an uneasy relationship with governments. They aspire to be neutral conduits of data and to sit outside or above politics.

‘But increasingly their services not only host the material of violent extremism or child exploitation, but are the routes for the facilitation of crime and terrorism.

‘However much they may dislike it, they have become the command and control networks of choice for terrorists and criminals, who find their services as transformational as the rest of us.’

Officials say the job of spy agencies has become ‘much harder’ over the past 18 months as US firms become less willing to hand over data. Whitehall sources say the companies have changed how they behave in response to the Snowden revelations.

His exposure of how GCHQ and America’s National Security Agency were able to tap into online data has made companies nervous about protecting their own reputations, they said.

Writing in the Financial Times, Mr Hannigan said mobile technology and smartphones have increased the options available to terrorists ‘exponentially’.

GCHQ director Robert Hannigan (left) said internet firms needed to allow the state to police on-line traffic. NSA leaker Ed Snowden (right), revealed intensive collaboration between spy agencies and internet companies

What they know... A National Security Agency slide leaked by Snowden reveals the scale of the access that state spies have to internet users' personal communications and information

He said: ‘Techniques for encrypting messages or making them anonymous, which were once the preserve of the most sophisticated criminals or nation states, now come as standard. These are supplemented by freely available programs and apps adding extra layers of security, many of them proudly advertising that they are “Snowden approved”.

‘There is no doubt that young foreign fighters have learnt and benefited from the leaks of the past two years. The challenge to governments and their intelligence agencies is huge and it can only be met with greater co-operation from technology companies. Terrorists have long made use of the internet. But IS’s approach is different in two important areas.

‘Where Al Qaeda and its affiliates saw the internet as a place to disseminate material anonymously, IS has embraced the web as a noisy channel in which to promote itself, intimidate people, and radicalise new recruits.’

Intelligence sources have previously warned how Snowden’s revelations – mainly published by the Guardian in the UK – have made it harder to track the movements and tactics of IS because they have become better at knowing how to avoid detection.

Mr Hannigan went on: ‘For our part, intelligence agencies such as GCHQ need to enter the public debate about privacy.

Where Al Qaeda and its affiliates saw the internet as a place to disseminate material anonymously or meet in 'dark spaces', Isis has embraced the web as a noisy channel in which to promote itself, intimidate people, and radicalise new recruits. GCHQ director Robert Hannigan

‘We need to show how we are accountable for the data we use to protect people, just as the private sector is increasingly under pressure to show how it filters and sells its customers’ data.

‘GCHQ is happy to be part of a mature debate on privacy in the digital age. But privacy has never been an absolute right and the debate about this should not become a reason for postponing urgent and difficult decisions. To those of us who have to tackle the depressing end of human behaviour on the internet, it can seem some technology companies are in denial about its misuse.

‘I suspect most ordinary users of the internet are ahead of them: they have strong views on the ethics of companies, whether on taxation, child protection or privacy; they do not want the media platforms they use with their friends and families to facilitate murder or child abuse.

‘They know the internet grew out of the values of Western democracy, not vice versa. I think those customers would be comfortable with a better, more sustainable relationship between the agencies and the technology companies.’

Hazel Blears, an ex-Home Office minister who sits on Westminster’s Intelligence and Security Committee, recently said IS militants would be ‘very much aware’ of what Snowden had made public.