Isis: Defence Secretary Michael Fallon predicts two to three-year campaign in Iraq

MPs to vote on measures tomorrow

The option of UK air strikes against Isis in Syria has been left open (Getty Images)

The Government kept the option of UK air strikes against Isis in Syria open today, even though MPs are set to vote to limit action against the jihadist group in Iraq.

Defence Secretary Michael Fallon said it was the new Iraqi government that the UK needed to help first. In an interview with Parliament’s The House magazine, he accepted that Syria was “different” but added: “We shouldn’t resile from direct military action if Isis is going to be defeated. This isn’t about containment. This is about the defeat of Isis.”

Mr Fallon suggested that UK armed forces will be engaged in Iraq for a “long haul” of at least “two to three years".

In an emergency Commons debate tomorrow to be opened by David Cameron, an overwhelming majority of MPs is expected to authorise air strikes in Iraq and they could begin within hours of the vote. The Cabinet discussed its strategy today.

Mr Fallon’s remarks will fuel fears among some MPs about “mission creep” in which UK intervention spreads to Syria because Isis operates there and does not recognise the border with Iraq.

Ed Miliband, the Labour leader, will support action in Iraq but will make clear that he is not giving a black cheque for it to extend to Syria. There are legal doubts about action in Syria because, unlike Iraq, its government has not requested help in the fight against Isis.

The Liberal Democrats are also limiting their backing to bombing in Iraq. Nick Clegg, the Deputy Prime Minister, told LBC radio today that any proposal to take action in Syria would be put to a fresh vote in Parliament.

“If we were to decide to play a fuller role behind Iraq and in Syria, then we’d go back to Parliament for another debate and a vote,” he said.

In an echo of the 2003 Iraq War, Downing Street published a summary of the legal advice on intervening in Iraq given by the Attorney General Jeremy Wright to today's Cabinet meeting, which backed air strikes.

It said: "The Government is satisfied that the consent of Iraq provides a clear and unequivocal legal basis for the deployment of UK forces and military assets to take military action to strike Isis sites and military strongholds in Iraq.

"The UK will conduct military action in accordance with applicable international law, including international humanitarian law."

The Cabinet agreed the Commons resolution to be debated tomorrow, which says: "This motion does not endorse UK air strikes in Syria as part of this campaign, and any proposal to do so would be subject to a separate vote in Parliament. [The] Government will not deploy UK troops in ground combat operations."