Max Hill, who has recently taken on the role of the Government’s independent reviewer of terrorism legislation, claimed Islamic State were planning ”indiscriminate attacks on innocent civilians”.
Mr Hill, who worked as one of the UK’s leading terror prosecutors, claimed the threat of ISIS was an “enormous ongoing risk which none of us can ignore”.
Comparing ISIS to the IRA, Mr Hill said: “It is possible to point to distinctions in terms of the mindset, organisation and strategy of different terrorist groups and therefore it would be wrong to draw a simple comparison between Irish republicanism and the ideology of so-called Islamic State.
“But in terms of the threat that’s represented, I think the intensity and the potential frequency of serious plot planning – with a view to indiscriminate attacks on innocent civilians of whatever race or colour in metropolitan areas – represents an enormous on-going risk that none of us can ignore.
Mr Hill’s work as a prosecutor saw him help to convict terror plotters
“So I think that there is undoubtedly significant ongoing risk which is at least as great as the threat to London in the Seventies when the IRA were active on the mainland.”
Mr Hill’s work as a prosecutor saw him help to convict the plotters who attempted to strike London just days after the 7/7 attacks and break up terror cells in Britain.
Yet the terror expert believes the work of British intelligence was to thank for abating the tide of terror in the UK.
But the government watchdog he is concerned the threat is only getting worse as hundreds of Brits who left to fight for ISIS may return to the UK as the terror tyrants lose their ground war in Syria and Iraq
Mr Hill told the Sunday Telegraph: “It’s an enormous concern that large numbers – we know this means at least hundreds of British citizens who have left this country in order to fight – are now returning or may be about to return.
“Of course the imminent fall of Mosul and perhaps the prospective retaking of Raqqa are both bound to lead to a higher instance of returning fighters.
“Does that mean that the British public need to be immediately alarmed at a spike in terrorist activity within this country?
“The answer to that is, I don’t know, but it doesn’t follow as a matter of fact that those who chose to go to live or fight abroad will bring that fight back to this country.”
It comes after a new report warned Al Qaeda has been secretly planning a major resurgence in a bid to attack Britain and the West after Islamic State’s impending downfall.
An attack on the UK by the jihadi group made infamous by the 9/11 attack on New York’s Twin Towers in 2001 is “highly likely”, a terrorism threat report by Pool Re, Britain’s terrorism experts, has found.
Al Qaeda was believed to be on the “verge of strategic collapse” five years ago after founder Osama bin Laden and lead radicaliser Anwar al-Awlaki were killed.
However, its supporters have been utilising the Western allies’ fight on ISIS in the Middle East to grow in the Arabian Peninsula during the Yemen conflict.