His warning came as the man in charge of the UK's counter-terrorism unit said 'exceptionally high' numbers of extremists are being investigated.
Scotland Yard assistant commissioner Mark Rowley - the UK's national policing lead for counter-terrorism - admits a large part of their work is now based online.
Simon Barrett, a Christian and terrorism expert, told Premier's News Hour: "What we're seeing is an escalation in the threat of terrorism in the face of ISIS and particularly ISIS strategy of using social media in order to win to their evil cause, which is leading to an increasing radicalisation."
Officers say they have already foiled several potentially deadly attacks and arrested hundreds of terror suspects so far this year.
They say they have had to change the way they investigate terrorism.
Mr Barrett added: "It's not so much chatter on emails and email communications that we had before, going back to ten years ago.
"It's more the fact that we're seeing even more videos of suicide bombings [and] beheadings that are being used to glorify terrorism violence."
Meanwhile, four men who allegedly swore an allegiance to Islamic State have been charged with plotting a terror attack in London.
Scotland Yard says Tarik Hassane, 21, Suhaib Majeed, 20, Nyall Hamlett, 24, and Momen Motasim, 21, have all been charged with intending to commit acts of terrorism.
A fifth man, Nathan Cuffy, 25, has been charged with firearms offences.
The charges allege that the four men carried out "hostile reconnaissance" at Shepherd's Bush police station and White City Territorial Army Barracks.
They are also accused of taking an oath of allegiance to IS.