Iraq airstrikes imminent as PM seeks to widen war against Isis into Syria
British military action in Syria became more likely after MPs last night overwhelmingly approved airstrikes against Isis targets in Iraq.
Six RAF Tornados will launch attacks within days, after the Commons voted by a huge majority to approve intervention.
David Cameron made clear he wants to extend military involvement to Syria.
Despite MPs backing the motion by 524 to 43, yesterday's emergency debate became heated as fears were expressed of "mission creep" and others argued over whether to take military action in Syria as well as Iraq.
Twenty-four Labour MPs, six Tories and one Liberal Democrat voted against becoming involved in a new war in Iraq.
Rushanara Ali, a Labour education spokeswoman, resigned from the opposition front bench so she could abstain. Iain McKenzie was sacked as a Labour parliamentary aide after voting against.
Several MPs argued that it would be logical to extend airstrikes to Syria, pointing out that Isis, also known as Islamic State, does not recognise the border between the two countries.
Mr Cameron gave his clearest sign yet that he would like to join the US in hitting Isis in Syria. "I am very clear that Isis needs to be destroyed in Syria as well as in Iraq," he told the Commons. "I believe that there is a strong case for us to do more in Syria."
The Prime Minister admitted that Syria was a "more complicated" issue than Iraq, where the new government has formally requested UK military support.
He brushed aside legal doubts about action in Syria.
"I do not believe there is a legal barrier because I think that the legal advice is clear that, were we or others to act, there is a legal basis," he said.
One method could be for Iraq to request British help to combat Isis attacks launched from Syria, which could then allow intervention under the United Nations charter.
The motion approved yesterday promised MPs a fresh vote before any intervention in Syria, but Mr Cameron also kept open the option of authorising emergency action there.
In this case, MPs would be asked as soon as possible for retrospective approval, he said.
Mr Cameron would probably need Labour's support to win a majority.
A Labour spokesman said last night: "Without a clear plan for military activity in Syria, we are not giving the Government a blank cheque."
Ed Miliband is not ruling out action in Syria. He wants an attempt made at the UN to secure approval for action there, but is not making a UN resolution a condition of his support.
He wants the Prime Minister to spell out which countries would send troops to fight in Syria.
The Labour leader told MPs: "When we are not talking about being invited in by a democratic state, it would be better – I put it no higher than that – to seek a UN Security Council resolution. That is the highest multilateral institution of the world."
Ministers are starting to build a case for a wider campaign against Isis in Syria. Michael Fallon, the Defence Secretary, said: "Isis is based in Syria. That's where its headquarters are, that's where its resources, its people, are.
"They have crossed the border into Iraq and to deal with Isis you do have to deal [with] and defeat them in both Iraq and in Syria."
He added: "The Prime Minister made it clear that to defeat Isis we have to do it in both countries, so the logic follows.
"But we are not asking Parliament to do that at the moment, we are taking this in a calm, measured way, step by step. But it is clear to us that, obviously, Isis, in the end, has to be tackled on a broader front."
Several senior MPs spoke in favour of action in Syria.
Sir Richard Ottaway, the Conservative chairman of the Commons foreign affairs select committee, said: "The border between Syria and Iraq has virtually disappeared.
"It is a seamless conflict over two countries covering thousands of miles and presenting a vulnerability in Isis's stretched resources that we are not capitalising on."
Kenneth Clarke, the former Tory minister, said: "The legal case for intervention in Iraq is clear with its Government inviting us, and I think it is pretty clear in Syria because of the genocide and the humanitarian disasters being inflicted on that country."
Former Northern Ireland Secretary of State Peter Hain said: "Isis will never be defeated if it is constantly allowed to regroup from its Syrian bases."
Sir Menzies Campbell, the former Liberal Democrat leader, said: "The very factors that justify intervention in Iraq would be of equal weight in relation to Syria.
"Those are, to put it briefly, the barbarism that is being displayed, and the fact that regional stability is being heavily undermined."
Dennis Skinner, the veteran Labour MP, said: "There are two questions the Prime Minister has not put to himself: how long will this war last and when will mission creep start?"