The Government has been urged to strip British jihadists of their citizenship as reports emerged that intelligence services have identified the apparently British killer behind the horrific murder of an American journalist.

Former shadow home secretary David Davis dismissed suggestions that possible new laws, dubbed asbos for terrorists, would prevent Britons fighting for Islamic State (IS) and said they must instead be stopped from returning to the UK.

Lord Carey, former Archbishop of Canterbury, also called for Britons fighting for IS in Iraq and Syria to lose their passports.

Writing in the Mail on Sunday, Lord Carey said: "They should not have access to the privilege of travelling under a British passport . . . and they certainly should not be able to travel back with the barbaric and bloodthirsty skills they have gained.'

Home Secretary Theresa May is poised to bring in new laws to tackle British extremists in the wake of the horrific killing of US journalist James Foley by a jihadist with an English accent.

But Mr Davis said the G overnment's response to the crisis in Iraq had been 'tentative, uncertain, almost limp" and suggested the men heading overseas to fight were committing treason.

In an article for the Mail on Sunday, Mr Davis wrote: " Asbos for terrorists? It is hard to imagine the ISIS killers quaking in their boots."

He added: " Since these young men are in effect swearing allegiance to a hostile state, they should all forfeit their British citizenship - not just those who are dual nationals.

"Since this is an incredibly serious penalty, it should be done only after a proper public trial carrying all the public seriousness and opprobrium of a murder trial, because in many cases that is what it would be.

" As the Home Secretary reiterated yesterday, lawyers would say you cannot render someone stateless. Perhaps, perhaps not. Whitehall lawyers have been wrong before. Democracies have a right to defend themselves.

" IS is claiming to be a state. They can issue these young men with Islamic State passports if they so wish. It is not our problem that they would have trouble getting into any civilised country with them."

Meanwhile, MI5 and MI6 have worked out the identity of Mr Foley's killer, known as "Jihadi John", but none of the details have been disclosed, The Sunday Times reported.

Foreign Secretary Philip Hammond told the newspaper the killing was "an utter betrayal" of everything Britain stands for.

"It is horrifying to think that the perpetrator of this heinous act could have been brought up in Britain," he said.