To recap on this developing story, Jeremy Corbyn has said he cannot support the prime minister's case for air strikes against IS in Syria.

His letter to Labour MPs setting out his position comes just hours after David Cameron told the House of Commons today that extending military action against the extremist group from Iraq into Syria will "make us safer".

The prime minister denied claims it would make the UK a bigger target for terror attacks, as he made the case for military action, in the Commons.

He told MPs the UK was already a target for IS - and the only way to deal with that was to "take action" now.

Former Prime Minister Tony Blair says he agrees with David Cameron on taking military action in Syria, external. 

He says there are many MPs who also support air strikes in Syria.

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"Dear Colleagues,

The Prime Minister made a statement today to the House of Commons making the case for a UK bombing campaign against ISIS in Syria.

A copy of my response has already been circulated.

We've all been horrified by the despicable attacks in Paris and are determined to see the defeat of ISIS. Our first priority must be the security of Britain and the safety of the British people. The issue now is whether what the PM is proposing strengthens, or undermines, our national security. I do not believe that the PM today made a convincing case that extending UK bombing to Syria would meet that crucial test. Nor did it satisfactorily answer the questions raised by us and the Foreign Affairs Committee.

In particular, the PM did not set out a coherent strategy, coordinated through the UN for the defeat of ISIS.

Nor has he been able to explain what a credible and acceptable ground forces could retake and hold territory freed from ISIS control by an intensified air campaign.

In my view, the PM has been unable to explain the contribution of additional UK bombing to a comprehensive negotiated political settlement of the Syrian civil war, or its likely impact on the threat of terrorist attacks in the UK.

For these, and other reasons, I do not believe the PM's current proposal for air strikes in syria will protect our security and therefore cannot support it.

The shadow cabinet met today for an initial discussion and debated the issues extensively. We will meet again on Monday when we will attempt to reach a common view.

I will get in touch again when we know the timing of the debate and the vote.

Yours,

Jeremy"

Labour leader Jeremy Corbyn may be against air strikes in Syria, but according to shadow Northern Ireland secretary Vernon Coaker (a former shadow defence secretary) "a significant part" of the shadow cabinet and wider parliamentary Labour Party back military action. He has told BBC Radio Nottingham:

Jeremy Corbyn is writing to Labour MPs this evening to say that he cannot support the prime minister's proposal for extending UK air strikes against the so-called Islamic State group in to Syria, says the BBC's political editor Laura Kuenssberg

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Talking about the case for air strikes, former shadow attorney general Emily Thornberry says it's a complicated situation but cautions that politicians should "always stand back and ask" whether action would make things better.

She said she was trying to keep an open mind on the question, but she feels the prime minister hasn't answered key questions, including about who the ground troops will be.

Philip Hammond defends the figure of 70,000 Syrian opposition fighters on the ground in Syria. "We don't have precise figure but I think 70,000 is a good working figure," he tells BBC News, saying it's based on the "best assessments" and estimates.

What if Parliament doesn't support extending UK air strikes into Syria? The foreign secretary says it'll leave the world "a less safe place" and the UK more "exposed".

The Daily Politics

BBC News Channel

Foreign Secretary Philip Hammond says "it feels as though we are building a consensus now for military action in Syria". Any such action would be part of a package that included a humanitarian and political response, he adds.

Asked about the timing of a vote, he tells BBC News the PM wants to give MPs time to consider the case for military action. "Let's let the dust settle," he says, adding that Parliament will be in a stronger position next week to know whether there's a consensus in favour of bombing IS in Syria.

The Treasury says it is "not legitimate" to compare what new claimants will receive under Universal Credit in 2020 and what they would be entitled to now. In a statement, it said:

It added that the suggestion that tax credit cuts have been "postponed or transferred" into Universal Credit "is completely misleading". 

Image source, Getty Images

Former Scotland First Minister Alex Salmond has been criticised for unveiling his new portrait in Edinburgh on the day MPs discussed military action in Syria.

The SNP's foreign affairs spokesman was not in the House of Commons to hear Prime Minister David Cameron make his argument for air strikes.

Scottish Conservative leader Ruth Davidson believed Mr Salmond should have been at Westminster.

The SNP said the MP had been on constituency business.

More here.