A vote had been widely expected to take place in the autumn, after Mr Cameron made clear that he wants to extend RAF missions against the Islamic State terror group from Iraq into Syria, but will do so only if he can secure a “consensus” among MPs.
But reports suggested the PM has now abandoned plans to seek Commons approval for military action, because he could not be sure of obtaining the backing of enough Labour MPs to secure victory in the face of an expected rebellion by 20-30 Conservatives.
Unnamed Whitehall sources told The Times and The Guardian that the launch of Russian air strikes in September had also complicated the situation.
However, a Downing Street source said: “The Prime Minister’s position hasn’t changed. He’s consistently said that we would only go back to the House on this issue if there was clear consensus and that remains the case.
“Meanwhile, the Government continues to work to bring the conflict to an end in Syria and we are working closely with our allies to inject greater momentum into efforts to find a political solution, which we’ve always said will be the way to bring this war to an end and give Syria hope for the future.”
The claims emerged as an influential Commons committee cautioned that the PM should not ask MPs to back military action against IS in Syria until he can show there is a clear plan both to defeat the jihadists and to end the bloody civil war in the Middle East state.
In a major blow to the Prime Minister’s hopes of extending the British mission, the Tory-led Foreign Affairs Select Committee said it was “not yet persuaded” that Mr Cameron would be able to address their concerns.
The strongly-worded report warned that RAF strikes would only have a “marginal effect”, but could be a “distraction” and compromise efforts to find a diplomatic solution to the crisis.
The MPs acknowledged the “humanitarian and security catastrophe” in Syria meant there was a “powerful sense that something must be done”, and that defeating IS was a “necessary goal for the UK”.
But they said: “We believe that there should be no extension of British military action into Syria unless there is a coherent international strategy that has a realistic chance of defeating Isil and of ending the civil war in Syria.
“In the absence of such a strategy, taking action to meet the desire to do something is still incoherent.”
The MPs warned of “further reputational damage” to the UK if the legal basis of air strikes is not clear, and recommended seeking a United Nations Security Council resolution, which is likely to be hard to achieve given the impasse between the West and Russia on the issue.
They said a bombing campaign would require “reliable” allies on the ground to identify targets and hold ground, but the chaotic situation meant “these would not be easy to find”.
And they demanded explanations of how military action would improve the chances of success against IS, how it would contribute to a transition plan in Syria and whether RAF strikes would have support from regional powers including Turkey, Iran, Saudi Arabia and Iraq.
“We are not yet persuaded that it is possible for the Government to provide a satisfactory explanation of these points at present,” the committee’s report said.
“Until it can, we recommend that it does not bring to the House a motion seeking the extension of British military action to Syria.”
Committee chairman Crispin Blunt said: “We are concerned that the Government is focusing on extending airstrikes to Syria, responding to the powerful sense that something must be done to tackle Isil in Syria, without any expectation that its action will be militarily decisive, and without a coherent and long-term plan for defeating Isil and ending the civil war.”
But Foreign Secretary Philip Hammond said: “Defeating Isil and ending the Syrian conflict are two faces of the same problem that Britain is working tirelessly with our international partners to overcome.
“Britain remains committed to using every tool available to save lives and create the conditions for peace in Iraq and Syria.”
Shadow foreign secretary Hilary Benn said: “The narrow question of whether or not we should carry out air strikes against Isil/Daesh targets in Syria appears to have been the focus of the Government’s attention, at the expense of developing a coherent political strategy for ending a civil war that has claimed 200,000 innocent civilian lives, the majority at the hands of Assad’s forces. This will only happen through a negotiated settlement led by the United Nations.”
A Labour Party spokesman later said: “Labour would, of course, listen to representations from the Stop the War Coalition, as it would from other external bodies, before coming to any decision.”