Cameron warns ISIL is planning to attack UK as he sets out argument for bombing

He insisted there was strong legal justification for extending the current military action in Iraq, on grounds of self-defence and the recent UN Security Council resolution.

However there has been concern from MPs about the Prime Minister’s claim that there are currently 70,000 moderate forces on the ground that would UK strikes.

Members queried the capabilities of the Free Syrian Army and Peshmerga Kurd fighters to hold land from IS, and it’s also unclear whether 70,000 allied ground troops is estimated to be enough to take on IS without an idea of the extremists’ numbers.

The Government is now waiting for guidance from Labour’s chief whip, Donacaster Central MP Rosie Winterson, on whether the party would support airstrikes and Labour leader Jeremy Corbyn was briefed by the Government on the case for action last night.

There will also be a meeting of the shadow cabinet today to try and hammer out an agreement on how to approach a vote, which is understood to be timetabled before Christmas.

Mr Cameron repeated today that he would not call a vote in the Commons until he was sure there was a clear majority in favour of action as defeat would be a “publicity coup” for IS.

He told MPs that Britain must judge whether inaction in Syria carried greater risks than action.

And he added: “The military advice and diplomatic advice and the security advice all says that the risks of inaction are greater.”

Addressing concerns that joining airstrikes in Syria would put Britain at risk of Paris-style terror attacks, the PM said that security agencies agreed that the UK was already “in the top tier of countries that Isil is targeting”.

Mr Cameron said his response to Syria would be ‘Isil-first’ and have four strands, a counter extremism strategy, a diplomatic process, military action and post-conflict stabilisation of Syria which would involve a £1bn British grant to rebuild the country.

He also set out how British military hardware, including the Royal Air Force’s Brimstone missiles, Raptor Pods and Reeper drones, would be of great assistance to the coalition of forces, and how America has called on the UK for help and he respected their relationship as ‘oldest friends’.

Conservative MP for Brigg and Goole, Andrew Percy, told the House of Commons today that he had been convinced by the Prime Minister’s case for action despite voting against strikes against Assad in 2013.

Two years ago, thirty Conservative MPs rebelled including Jason McCartney, Colne Valley; David David, Haltemprice and Howden; Philip Davies, Shipley; and Martin Vickers, Cleethorpes.

Labour leader Jeremy Corbyn did not immediately make clear whether he would tell his MPs to back military action in a Commons vote.

Mr Corbyn warned of “unintended consequences” if Britain got involved in military action in Syria in the same way it had in Iraq and Afghanistan, and urged the PM to make clear whether he was ruling out the use of UK forces on the ground.

Mr Cameron said he believed the presence of Western boots on the ground in Syria would be “counter-productive” and assured him: “We are not going to deploy British combat forces.”

The Labour leader said there was “no doubt” that IS had imposed a reign of terror in parts of Syria and Iraq and posed a threat to British people.

But he added: “The question must now be whether extending the UK bombing from Iraq to Syria is likely to reduce or increase that threat, and whether it will counter or spread the terror campaign Isil is waging in the Middle East.”

Labour’s Hull North MP Diana Johnson also queried the legality of carrying out air strikes as the UN resolution 2249 that was passed by the Security Council on Saturday, isn’t the same as a UN Chapter 7 resolution which specifically mentions military action.

She said the UN backing the Prime Minister speaks of as supporting his case ‘does not provide the unambigious permission to use military action’.

Mr Cameron said: “I would say it is fairly comprehensive and I read out some of the key terms in it and it was unanimously adopted and it’s got that key sort of Chapter 7 language in it about ‘all necessary mearsures’ even though it isn’t Chapter 7 itself.

“Look in all these things one can seek perfection, or one can say we have UN backing, we have a political process, we have allies asking to us act, we have the advice from our intelligence and security forces about the dangers that we face.

“In the end, with all that, there comes a decision and that’s the decision I think we need to take.”

The Scottish National Party’s leader in Westminster Angus Robertson said that his party’s 56 MPs will not vote for airstrikes in Syria unless they are convinced that there is effective ground support and a fully-costed plan for post-war reconstruction.

But the chairman of the Commons Foreign Affairs Committee - which earlier this month released a report urging caution over Syria - said he was now ready to back military action.

Crispin Blunt said: “It is now my personal view that, on balance, the country would be best served by this House supporting his judgments that the UK should play a full role in the coalition, to best support and shape the politics, thus enabling the earliest military and eventual ideological defeat of Isil.”