2:08pm Update: Against the expectations of some, Jeremy Corbyn has given Labour MPs a free vote on Syria. The leader's decision avoids the threat of shadow cabinet resignations but will make it far easier for David Cameron to achieve the "clear majority" he seeks for air strikes. Corbyn will state, however, that it is party policy to oppose air strikes, a stance backed by the membership. But as before, shadow cabinet ministers will argue that the terms of the Labour's Syria conference resolution have been met and that policy, if anything, should be to support military action.

Corbyn will also call on Cameron to delay the vote until Labour's concerns, such as the role of ground troops, have been addressed. But the PM will press ahead with a decision this Wednesday.

A free vote is, many MPs believe, the least worst solution to a divided party. But several shadow cabinet fear, in the words of one, that not taking a collective stance on a matter of war leaves Labour "unfit for government".

Corbyn has written to Cameron demanding a "full two day debate" on Syria. That would mean the government delaying the vote until after Wednesday.

Dear David As of this morning we have not had a clear proposal from the government on when you plan to bring forward a motion to the House on air strikes in Syria or on arrangements for the debate. In the view of the Opposition on a matter of such critical importance there must be full and adequate time for any debate in the House and only a full two day debate would ensure time for all Members who wish to participate to be able to do so. As has happened previously a one day debate would inevitably lead to important contributions being curtailed. It is incumbent on us all to ensure the country feels there has been the fullest parliamentary discussion of what you have rightly described as a highly complex situation. In addition the debate would be much better informed by views from the Foreign Affairs and Defence Select Committees following your recent statements. Please can you provide an assurance that any proposal the government brings forward will be on the basis that there will be a two day debate in the House of Commons. Yours sincerely Jeremy Corbyn MP Leader of the Opposition

Ahead of the shadow cabinet meeting at 2pm, frontbenchers told me that they still didn't know whether Jeremy Corbyn would allow them a free vote on Syria. Some of the Labour leader's allies, such as John McDonnell, are arguing for a free vote over air strikes but others are pushing Corbyn to whip the party in line with his anti-war position, for which, they emphasise, he has a mandate.

The release by Labour at 12:44pm of a poll showing that 75 per cent of party members (based on an initial sample of 1,900) oppose military action is indicative of the latter group's growing strength. They are emboldened by increasing hostility among the shadow cabinet, the parliamentary party and activists to air strikes. Several shadow cabinet members who were previously undecided have told me they would now likely vote against interventions.

Frontbenchers warn that a whipped vote would lead to resignations, including potentially the entire shadow defence team. Committed supporters of air strikes include deputy leader Tom Watson, shadow foreign secretary Hilary Benn, shadow justice secretary Charles Falconer, shadow culture secretary Michael Dugher and shadow Commons leader Chris Bryant. But rather than a free vote or a whipped vote, Corbyn may opt for something in between. One frontbencher told me that the party could be whipped against but that "collective responsibility could be suspended". Labour would be officially opposed to air strikes but the consequences that would usually result from that decision would not occur. That, MPs say, would certainly be "new politics".