The number of terrorist attacks inspired by Isis has increased tenfold over the last year, the Defence Secretary has said.
Michael Fallon, setting out the Government's argument for extending British air strikes into Syria, told MPs that last year there had been 15 attacks around the world that were inspired or directed by Isis last year but in 2015 there had already been 150.
He said that was another reason for bombing the group's stronghold in northern Syria as he appeared in front of the Defence Committee alongside the deputy head of the Armed Forces.
Ministers have faced questions over David Cameron's claim that there were 70,000 moderate Syrian fighters who could seize Isis-territory following air strikes, a figure that was described as "magical" by the Tory chairman of the Defence Committee Julian Lewis.
Challenged on this figure, Lieutenant General Gordon Messenger, said there was a "spectrum of extremism” within Syria and could not confirm whether the figure included fighters from Islamist groups the Islamic Front or Ahrar Al Sham.
The Government has published the motion on bombing Isis in Syria that MPs will debate for 10 and a half hours on Wednesday.
It declares that Isis poses an "unprecedented" and "direct threat" to the UK and asks MPs to support the Government and Armed Forces in "taking military action, specifically airstrikes, exclusively against Isil in Syria".
The motion pledges not to deploy UK troops on the ground in Syria and commits the Government to giving MPs progress updates every three months.
In pictures: Syria air strikes (2014)
In pictures: Syria air strikes (2014)
Syrian citizens check a damaged house that targeted by the coalition airstrikes, in the village of Kfar Derian, a base for the al-Qaida-linked Nusra Front, a rival of the Isis group, between the northern province of Aleppo and Idlib
A Syrian boy (L) looking at a destroyed car that activists say was targeted by the coalition airstrikes, in the village of Kfar Derian, a base for the al-Qaida-linked Nusra Front, a rival of the Islamic State group, between the northern province of Aleppo and Idlib
Parts of a missile that activists say was fired by coalition airstrikes, in the village of Kfar Derian, a base for the al-Qaida-linked Nusra Front, a rival of the Isis group, between the northern province of Aleppo and Idlib
Tthe guided-missile destroyer USS Arleigh Burke (DDG 51) launching Tomahawk cruise missiles against Isis targets
The USS Arleigh Burke (DDG 51) launches a Tomahawk cruise missiles in the Red Sea, to conduct strike missions against Isis group targets in Syria
The guided-missile cruiser USS Philippine Sea (CG 58) launching a Tomahawk cruise missile against Isis targets in Syria, as seen from the aircraft carrier USS George H.W. Bush (CVN 77) in the Arabian Gulf
US navy sailors standing watch on the bridge while Tomahawk cruise missiles are launched against Isis targets in Syria, aboard the guided-missile cruiser USS Philippine Sea (CG 58), in the Arabian Gulf
The US-led airstrikes in Syria against Isis targets in and around the city of Raqqa
A fighter from the Isis group holds a piece of what the IS is saying is a US drone that crashed into a communications tower in the Syrian city of Raqqa
Fighters from the Isis organisation pray at the spot where the jihadist group said a US drone crashed into a communications tower in the Syrian city of Raqqa
Fighters from the Isis group load a van with parts that they said was a US drone that crashed into a communications tower in the Syrian city of Raqqa
Fighters from the Isis group load a van with parts that they said was a US drone that crashed into a communications tower in Raqqa
Fighters from the Isis group gesture as they load a van with parts that they said was a US drone that crashed into a communications tower in Raqqa. A US-led coalition on carried out its first air strikes and missile attacks against jihadist positions in Syria, with Damascus saying it had been informed by Washington before the operation began
A Syrian man rides his bike past a communications tower that was destroyed after a US drone crashed into it, according to fighters with the Isis group, in the Syrian city of Raqqa
People inspect a shop damaged after what Isis militants say was a U.S. drone crashed into a communication station nearby in Raqqa
A man holds the remains of what Isis militants say was a U.S. drone which crashed in Raqqa
Resident gather in the back of a van the remains of what Isis militants say was a drone which crashed in Raqqa
A man inspects the remains of what Isismilitants say was a U.S. drone which crashed into a communication tower in Raqqa
A man inspects the remains of what Isis militants say was a U.S. drone which crashed in Raqqa
Speaking to the Defence Committee on the eve of the crunch vote, Mr Fallon said: "The nature of the campaign against Isil has begun to change as we have begun to change as we have begun to have had some success in Iraq.
"But the threat from Isis has intensified. Let me put it this way: there were some 15 Isil-inspired attacks - either Isil-inspired or Isil-directed - there were some 15 around the world last year.
"This year there have already been 150 and we've another month to go. So the threat has intensified."
Mr Fallon insisted that the Government's estimate of 70,000 moderate Syrian fighters on the ground in Syria “excludes those on the extreme side” such as the Al Nusra Front, the Syrian branch of Al Qaeda.
However, he said there were not “all in one place” or “a new model army, drilled outside the walls of Raqqa”.
“Is there a single commander who can weld all this together as Lawrence of Arabia tried to do 100 years ago – that I’m not sure,” he added.
“They are spread through Syria: over 20,000 in the Free Syrian Army [FSA] in the north, around 20,000 in the Southern Front commanded by [FSA commander] al Zoubi. There are groups throughout Syria that add to give you the overall figure of 70,000.”
Lieutenant General Messenger said the 70,000 were “not a coherent force” but said it would be wrong to consider them “a rag-tag army”.
“Those who are seen to be inside the 70,000 are those that are seen to be moderate, those that we are prepared to accept might be part of a political process,” he said.
He added: “Their principle motivation is one of defending their communities and self-preservation against whoever is fighting them.
“We don’t want to directly link airstrikes at the heart of ISIL with the idea that there is an imminent ground force about to exploit the effect of that. We can say that by applying pressure to ISIL we can relieve pressure on those moderate oppositions.”