Experts today say the Paris attacks have strengthened the case for air strikes in Syria as David Cameron signalled plans for a fresh Commons vote on UK intervention.

The Prime Minister told MPs yesterday that Britain should attack the "head of the snake".

"After the horror must come our resolve and determination to rid the world of this evil," he said.

He pledged to bring forward a "comprehensive" strategy to win support for bombing Islamic State (IS) militants in Syria as well as Iraq.

Sources said that details of the plan would be published within a fortnight.

MPs dramatically voted against military action in Syria in 2013, in what was seen as a humiliating Commons defeat for Mr Cameron.

The Conservative leader has repeatedly said that he wants another vote but that he would not push the issue until he feels felt there was a consensus in favour of action.

Tory sources believe that horrific events in Paris on Friday night have reduced the number of Conservative backbenchers who would vote against action, and increased the number of Labour MPs who would support strikes.

A new report by a leading defence think tank also says the Paris attacks have strengthened the case for UK intervention.

The Royal United Services Institute (Rusi) also predicts that pressure will now build to resolve the issue "one way or another".

But Alex Salmond, the SNP's foreign affairs spokesman, warned that Mr Cameron had not yet made a convincing case that intervention in Syria would make a "material" difference.

He also suggested that SNP MPs' would support action only if there was a mandate from the United Nations.

Labour leader Jeremy Corbyn also warned that any military action should be legal and have the support of the international community, including the UN.

Meanwhile, the Liberal Democrat leader Tim Farron warned against the UK finding itself embroiled in another conflict like the Iraq War.

The Rusi report says that the case for UK action is “stronger now than it was when the anti-(Islamic State) military coalition was first formed in September 2014...especially after the attacks on France, pressure will now build to resolve this issue one way or another.”

The document's author Professor Malcolm Chalmers suggests that “in the wake of the Paris attacks, ministers will also be highly sensitive to comparisons with France.”

But the report warns against overstating the benefits of air strikes.

The UK could provide specialist capabilities that US forces do not currently have, but British involvement would not “be strategically transformative” it adds.

Any UK campaign would also need to be based on the assumption that it may have to be sustained over several years, according to the report.

Earlier this year a report by the Commons Foreign Affairs Select Committee expressed serious doubts about UK air strikes.

Yesterday Crispin Blunt, the Conservative MP who chairs the committee, said: "I think we’re beginning to work towards the kind of international plan that will mean we’ve got a military task that we can achieve, and the military task is defeating [IS] in Syria and Iraq."

Earlier, Mr Cameron told MPs that IS, who have claimed responsibility for the French attacks, represented a "direct and growing threat" to the UK.

He said: "Raqqa, if you like, is the head of the snake. Over Syria we are supporting our allies - the US, France, Jordan and the Gulf countries - with intelligence, with surveillance and with refuelling. But I believe, as I have said many times before, we should be doing more.

"We face a direct and growing threat to our country and we need to deal with it not just in Iraq but in Syria too."

He warned that Britain could not protect its people "by sitting back and wishing things were different" or by letting other nations "carry the burden".

Meanwhile, Angus Robertson, the SNP's Westminster leader, said it appeared that "momentum" was building around talks to secure a Syrian ceasefire.

The Ministry of Defence also announced that RAF Tornado fighter jets have bombed more than 30 Isis militants who were attacking Kurdish forces in Iraq.