Cameron edges closer to Syria airstrikes as support grows on both sides of Commons

After the Iraq conflict and British intervention in Afghanistan, it was never going to be easy. But slowly and surely, David Cameron appears to be building sufficient parliamentary support for what could be the biggest decision of his premiership: to take part in airstrikes against Islamic State targets inside Syria.

There is, as yet, no date for a parliamentary vote, and Cameron insists he will only set one if and when he is sure he will win it. The PM remains cautious as he tiptoes along the road to war. He was badly burned in 2013 when he failed to gain parliamentary approval for airstrikes against Syrian president Bashar al-Assad, and wants no repeat of that.

Cameron will also want to avoid at all costs the same fate as Tony Blair, whose reputation and legacy has been stained by his decision to take the country into what many see as a disastrous war in Iraq.

But the atrocities in Paris and those on Friday in Mali, which have left about people 150 dead, have tilted the balance and shifted the parliamentary mood.

By the end of this week, the prime minister will respond to concerns about military action expressed by the all-party foreign affairs select committee, and effectively set out his case for war. If he puts a convincing case, and enough Labour MPs and Tory doubters are convinced, events could move fast.

Many Labour MPs and a significant minority of Tories who had harboured misgivings appear, already, to be moving in favour. Even the SNP leader, Nicola Sturgeon, has said in recent days that she will listen with an open mind to any case for military strikes that Cameron makes.

The prime minister will travel to Paris on Monday for talks with President François Hollande. They will focus on counter-terrorism cooperation and the fight against Isis in Syria and Iraq. Crucially, they will meet knowing that a powerful international consensus is building.

Evidence of the extent of international resolve came on Friday night, when the UN security council unanimously called on all its members to take “all necessary measures” against Isis, which it described as “a global and unprecedented threat to international peace and security”. While it did not provide an explicit legal basis for military action and did not invoke the section of the UN charter authorising the use of force, its declaration will be seen by most lawyers as a clear green light for airstrikes.