The man unmasked as Isis executioner Jihadi John is just one of many extremists who have “slipped through the net” under MI5’s watch, critics have claimed.
Mohammed Emwazi was known to security services for six years before he apparently appeared on an Isis video beheading American journalist James Foley in August.
In a series of 2010 emails he revealed that he considered suicide to escape spies and already felt like a “dead man walking” but still managed to flee to Syria two years later.
David Davis, the Conservative former shadow Home Secretary, said the fact he was allowed to escape and become Isis’ Western poster boy showed MI5 tactics were “ineffective”.
“Given the numbers who appear to have slipped through the net, it is legitimate to ask: how many more people must die before we start to look more closely at the strategy of our intelligence services?” he wrote in The Guardian.
Mr Davis listed one of the 7/7 bombers, Mumbai attackers and Lee Rigby murderer Michael Adebolajo in a “worrying pattern” of Islamist extremists who were able to commit atrocities despite being known to MI5.
Relying on interference rather than imprisonment “leaves known terrorists both to carry out evil deeds and to recruit more conspirators”, he claimed.
The Coalition Government’s changes to laws aiming to restrict the activities of suspected extremists have also been blamed for allowing would-be terrorists to maintain their networks.
Lord Carlile, the former independent reviewer of anti-terror laws, suggested that Emwazi might have been prevented from joining the so-called Islamic State if restrictions on suspects had not been relaxed.
“Had control orders been in place, in my view there is a realistic prospect that Mohammed Emwazi, and at least two of his associates, would have been the subject of control orders with a compulsory relocation,” he told Sky News.
“If that had been the case, he would not have done what he's done in recent times,” the Liberal Democrat peer added.
Three members of Emwazi’s network were reportedly subject to control orders brought in by the last Labour government, which meant they had to live outside London in 2011.
But when those orders were scrapped by the Coalition and replaced by “Tpims” – Terrorism Prevention and Investigation Measures – they were allowed to return to the capital and get back in contact with Emwazi and fellow extremists.
Two of the men on these weakened orders later absconded and Emwazi is believed to have fled to Syria shortly afterwards.
Powers to force suspects to move to another part of the country to prevent contact with co-conspirators have since been restored.
Lord Carlile's successor, David Anderson QC, dismissed similar criticisms made by London Mayor Boris Johnson as a “false debate” because the full control order regime was available until the end of 2011 and some of those associated with Emwazi had been subject to them.
Both the Prime Minister and Home Secretary rallied to the defence of MI5 and intelligence agencies, which a human rights group director suggested had driven Emwazi to extremism with their treatment.
Asim Qureshi, research director of Cage, claims Emwazi was interrogated by MI5 and subjected to security agency harassment before becoming a militant.
Addressing the Conservative Party's Welsh conference, Theresa May issued an impassioned defence of the way security services were addressing the danger posed by Islamist extremism and other threats.
“You might not see the work they do. You might not know the risks they take. You might not be told about the plots they stop,” she said.
"But these remarkable men and women are true heroes. And they deserve the support and respect of every single one of us."
The former head of MI6 also hit back at claims that the security services played a role in Emwazi's radicalisation.
Sir John Sawers, head of MI6 from 2009 to 2014, called arguments that harassment drove him to join Isis "very specious".
"The idea that somehow being spoken to by a member of MI5 is a radicalising act, I think this is very false and very transparent,“ he told BBC Radio 4's Today programme.
Sir John said there were thousands of people of concern to the intelligence agencies and there had to be a balance in the way they were dealt with.
"They're doing their professional job by being aware of these people. But there are probably several thousand of these individuals of concern and the numbers are rising as more people go to Syria and Iraq and are radicalised out there," he added.
"And no one is talking about rounding up all these people or keeping 100 per cent coverage, there's just not the resources to do that and it would be contrary to our principles of human rights to do that...so you do have to find a balance in there."
Nigel Farage said he believed Britain's involvement in wars in Iraq, Afghanistan and Libya had increased the danger of terrorism and the money should instead have been spent on boosting security services in this country.
"I think all these foreign wars have probably made things worse rather than better,“ he told BBC Breakfast. "There is an enemy within this country - a fifth column, as I have called it before.
“We have got to deal with it.”
Parliament’s Intelligence and Security Committee will be investigating how Emwazi slipped out of the country and why MI5 could not prevent his radicalisation.
Additional reporting by PA
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