Jeremy Corbyn has "shifted" public opinion away from the "case for war", an aide has claimed as it emerged the Labour leader will speak against bombing Syria in Parliament while his Shadow Foreign Secretary will make the opposite case for airstrikes.
The Labour leader today said he would give his MPs a free vote if David Cameron calls the House of Commons to back his case of bombing raids targeted at ISIL extremists, but also that the party policy remains opposed to airstrikes.
Mr Corbyn is basing his position on the Prime Minister failing to satisfy a motion agreed at the Labour party's conference in Brighton in October, which sets out tests - including a UN mandate – before the party would consent to the raids.
However, a majority of Labour frontbenchers, including Shadow Foreign Secretary Hilary Benn, believe the conditions of the conference motion have been met, and therefore support the case for expanding the RAF's involvement from Iraq to Syria.
A senior Labour source confirmed Mr Corbyn would speak at the Dispatch Box in the Commons making the case against UK military action, while Mr Benn would argue for.
Speculation has been rife that the Government wants to hold a vote on Wednesday, but Labour has called for a two-debate day before any vote should take place, which could push it back if the Prime Minister agrees.
The senior Labour source said Mr Corbyn had "turned" Labour Party, media and public opinion since formally declaring his opposition to Syria raids in a letter last week.
He also denied the position made Labour appear "shambolic", though he did say: "It's certainly unusual, but we've known all along there are different views."
He said: "(Jeremy) will be leading the opposition to the Government's case for war, which he and many others don’t think has been satisfactorily made.
"Everybody will be basing themselves on Labour's policy, which was agreed at party conference. It had four or five conditions without which there can be no question of Labour supporting military action in Syria. Some people think they have been met, but Jeremy certainly doesn’t."
He went on that in "the public, media and politics" that "opinion has shifted away from the case for war and towards the position Jeremy Corbyn had set out, leading the case against the rush to war that Cameron had laid out on Thursday".
He added: "(Jeremy Corbyn) was elected on a landslide a platform that included as one of its key planks a demand for a new kind of foreign policy, including opposition to the succession of disastrous wars in the Middle East. That is a key part of his leadership. He is offering a lead, but taking into account views of the shadow cabinet."
Mr Corbyn today published his survey based on 100,000 replies that suggests 75% of respondents oppose bombing Syria, though critics have questioned the legitimacy of a poll using a "random sample" of 1,900 replies, arguing it was self-selecting.
However, HuffPost UK understands that Mr Corbyn informed his colleagues that party whips had assessed that 43% of Labour MPs wanted to vote to bomb ISIL in Syria - 99 of its 231 MPs.
Labour MPs are facing pressure from grassroots campaigners to oppose the Government's call, with some commentators suggesting it is tantamount to bullying.
The Government's slim majority means it needs support from Labour MPs to approve the intervention.
The source said there was "no question of what the views of the Labour Party are" but a free vote reflects "deeply held views in some parts of the Labour party, particularly the Shadow Cabinet, on both sides of the argument".
"Since last Thursday there has also been a shift in the Shadow Cabinet towards Jeremy Corbyn's view," he added.