Iraq crisis: Hawks, doves, and owls choose their roosting spots in the Commons

Of the three Westminster leaders, Ed Miliband is under the greatest pressure from his own party

All three party leaders supported air strikes on Islamic State (Getty)

In 2003, it was simple: MPs were either for war in Iraq or against, doves or hawks. While the vote for military action against Islamic State (Isis) on Friday gave a majority of 481, the 2003 dividing lines have become blurred. There are the doves, against any action at all, the hawks who want to strike in Syria too, and those, like Ed Miliband, who back military action in Iraq but not Syria and would see themselves as wise owls – but whom are seen by others as "chicken-hawks".

Of the three Westminster leaders, Mr Miliband is under the greatest pressure from his own party. Labour's hawks, including members of the Shadow Cabinet, are concerned that Mr Miliband needs to set out a clearer position on whether to support RAF strikes against Syria. They blame Mr Miliband and Douglas Alexander, the Shadow Foreign Secretary, for fretting about UN resolutions before any action is taken against Syria. They point out that the QC Geoffrey Robertson, who had been a critic of the 2003 Iraq war, wrote in The Independent last week that military action against Syria as well as Iraq would be legal because Isis is not a sovereign state but a terrorist organisation and that President Assad's consent can be inferred. Mr Robertson wrote: "Syria has not complained and its consent to the attack on its most dangerous enemy can be inferred … however much Isis fighters may fantasise about a caliphate, they have no sovereign claim: they are international criminals, and any state or coalition of states is entitled to stop their rampage." He added that "the UK should support action to stop crimes against humanity in Iraq and Syria".

Mr Miliband's aides insisted yesterday that the Labour leader has not demanded a UN resolution, although he thinks it would be "better" to seek one. Hawk MPs say that Mr Miliband should have been clearer about not ruling out military action in Syria. Ian Austin, the Labour MP for Dudley North, told the Commons during Friday's debate that seeking a UN resolution over Syria risked "playing into Putin's hands" because Russia would be able to veto it.

Mr Austin said last night: "The border is not really very clear. If the objective is to deal with Isis then I don't think you could rule that out [air strikes on Syria]."

John Woodcock, the Labour MP for Barrow and Furness who urged the Commons to back military action, told Newsnight: "I think there is a clear case to go into Syria. We accept the legal case. There is no military sense in a campaign which stops in an imaginary border as far as the IS is concerned.

Six Tory MPs – including Mark Reckless, who defected to Ukip yesterday – voted against military action. They also included Richard Bacon, the deputy chairman of the Public Accounts Committee, who said last night: "I suspect that this is what Isis wants us to do. They want it to look like a battle against wicked imperialists from the West."

Mr Bacon added he felt it was still possible to get a UN resolution. He pointed out that House of Commons library research showed that there were 2.78 million soldiers across 18 Islamic countries, from which a peacekeeping force could be drawn. The South Norfolk MP added: "The overwhelming number of emails from my constituents show they think this is a bad idea."

But Mr Cameron also faces pressure from Tory hawks to go further and authorise military action against Syria – without a second Commons debate if necessary.

Nick Clegg, who opposed the 2003 invasion, could face an emergency motion at his party's conference. Activists are believed to be in favour of military action but deeply concerned about "mission creep" into Syria.