David Cameron’s hopes of building a cross-party consensus behind military air strikes against Islamic State forces in Syria were boosted after Labour said it would look “very, very seriously” at any government proposals to expand the bombing beyond Isis targets in Iraq.

Harriet Harman, the acting Labour leader, said everything must be done to stop the “horrifically oppressive” Isis, giving hope to Conservative interventionists who know that Labour votes would almost certainly be required to ensure a Commons majority in favour of extending the scope of military action.

She was speaking after Michael Fallon, the defence secretary, confirmed to MPs that the government favoured expanding the largely symbolic aerial bombing of Isis targets in Iraq to Syria.

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Fallon said: “There must be a full-spectrum response to deal with Isil [Isis] at its source in places such as Syria, Iraq and Libya. We know that Isil is organised and directed from northern Syria.”

The defence secretary also said the government would seek the approval of MPs before the current air campaign was extended from Iraq. But that approval was unlikely to be sought until the autumn, by which time Labour will have elected a new leader.

Cameron’s official spokeswoman said there was a need for “more thought, more deliberation, more time” before any decision to extend military action was taken. “The PM has long thought that Isil poses a threat to Britain and Isil needs to be destroyed in Syria as well as in Iraq,” she added.

Fallon tried to assure sceptical Tory MPs that any bombing campaign would not provide succour to Syria’s president, Bashar al-Assad, even though a weakening of Isis might be expected to benefit his regime. Assad, backed by Russia and Iran, has not tried to stop the US-led air campaign against Isis in northern Syria.



The Conservative chairman of the foreign affairs select committee, Crispin Blunt, and the chairman of the defence select committee, Julian Lewis, both voiced doubts in the Commons. Blunt said UK involvement in northern Syria would make no practical difference to the US-led campaign that has been under way for months. Lewis said the government had to choose whether Assad or Isis was the lesser of two evils, adding there was no good outcome to be had.

Cameron was scarred by his failure in the summer of 2013 to win Commons support for a bombing campaign against Assad to punish the Syrian leader for using chemical weapons on civilians, a vote that was lost after the prime minister failed to win over the support of Labour’s then leader, Ed Miliband.

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The prime minister has made clear to ministers that it would be pointless to call a vote without clear Labour support. Cameron’s 12-seat majority means he is vulnerable to losing a Commons vote if a handful of Tories rebel.



However, Labour sees a new request to bomb Isis forces in northern Syria as analogous to its existing support for targeted RAF air strikes, mainly involving Tornado GR4 aircraft, aimed at reining in Isis in Iraq.

Harman told ITV News: “Isil brutalise people, they murder people and they are horrifically oppressive. So everything that can be done to stop them must be done, and any proposals that the government bring forward which will help tackle the growing horror of Isil, of course we will look at them very, very seriously.”

Fallon said the RAF had flown nearly 1,000 missions, and 300 air strikes in Iraq had taken place.

Moderate Syrian forces also want coalition forces to impose a no-fly zone in Syria, preventing Assad from using barrel bombs, and to provide arms, something Britain continues to resist.

Vernon Coaker, the shadow defence secretary, made clear that Labour would not offer unconditional support. He told MPs: “The situation is totally different today compared with 2013, and we do no service to the country – or to anyone – if we are not clear about the difference between 2013 and 2015.”

Alex Salmond, the former Scottish first minister, highlighted the unease on all sides of the Commons at the prospect of a expansion of the bombing when he challenged Coaker, saying: “Unless I am very much mistaken [you] are preparing the ground to move the Labour party’s position to support air strikes in Syria.”



Coaker told Salmond: “If the military advice or the intelligence advice is that there is a headquarters directing terrorism across the world from parts of Syria and that people are conducting terrorist activities and killing British citizens who are on holiday on the directions of people in northern Syria – it would be right and proper to consider that and then to take whatever action was felt appropriate to deal with it.

“That is not the same thing as saying to the government: ‘It doesn’t matter what you say, we will support you.’”