It is always easy to persuade frightened people to part with their liberties. But it is always right for politicians who value liberty to resist attempts to increase arbitrary executive powers unless this is justified, not by magnifying fear, but by actual facts.

On Friday, the government announced that the imminent danger of jihadi attack meant Britain's threat level should be raised to "severe". Then, from the prime minister downwards, Tory ministers took to every available airwave to tell us how frightened we should be and why this required a range of new powers for them to exercise. For the record, the threat level in Northern Ireland has been "severe" for the past four years – as it was in all Britain for many years in the 1980s and 1990s, when the IRA threat was at its greatest.

I say this not to deny the threat from returning jihadis – though as the former head of counter-terrorism for MI6, Richard Barrett said on Saturday, this should not be overestimated. But rather to make the point that this is not a new threat. It is one we have faced before and one we know how to deal with – effectively, without panic and without a whole new range of executive powers that could endanger our liberties. Indeed, when it comes to facing threats, it was surely far more difficult to cope with IRA terrorists slipping across the Irish Sea than it is to stop jihadis returning from Iraq?

Of course, in these circumstances, the police and the security services will lead the clamour for more powers. They are charged by us to maintain our safety. It is natural they should want the most powerful weapons to enable them to do so. That's their job. But it is the job of politicians to act, not as cheerleaders for those demands, but as jealous protectors of our liberties who measure any demand for their reduction against necessity, supported by evidence.

David Cameron seemed to support this view when he said recently there should be no knee-jerk reactions. Since when, ahead of Monday's parliamentary debate, senior Tory ministers have indulged in a spasm of knee-jerking which would have made even St Vitus feel concerned. And Labour, frightened as always when it come to liberty and security, capitulates to the demand. It is difficult not to conclude that there is as much domestic politics at play here as there is national security.

I have no objection to what Nick Clegg has called specific, proportionate responses to strengthen our hand in tackling this threat. But these must be evidence based, careful of our liberties and sensitive to the need to keep moderate Islam on our side. For the wider threat of global jihadism will only be beaten if we can engage and work with the overwhelming majority of Islam who want to see their religion recaptured from the forces of darkness and medievalism that now threatens them. They, not western bombs and rockets, are our most powerful allies.

Here it is not Cameron's proposals that I fear, it is his rhetoric. He recently told us that this fight was about defending "western values". I cannot think of any phrase, short of those used by George Bush during the Iraq war, which more damages our ability to win this battle. For it at once confirms the jihadis' Manichean view that this is indeed a struggle between the west and them, while at the same time alienating those very Islamic moderates whose help we need most in defeating Isis and its cohorts. The truth is that this increasingly brutal and dangerous battle will not be won for our "western values" but for the universal values which underpin and unite all the world's great religions and philosophies – including, perhaps especially at this moment, Islam.

The point here, which the government is studiously missing, is that the best defence for Britain lies, not in action on the domestic front, but on the international one. The biggest danger we face is not returning jihadis, but a widening religious war which threatens, not just to engulf the Middle East and change its borders, but to spread across the entire global Islamic community with potential consequences for peace on a much wider scale.

I happen to believe that what is happening in the Middle East at the moment is a convulsion which will, in due course, play itself out as ordinary Muslims recapture their religion for its true values. But in the process there could be terrible suffering, the obliteration of borders, a widening regional war. And with Russia supporting Assad and Tehran, even the possibility of the great powers being sucked in on opposing sides.

With so many piles of tinder lying around in the littoral which stretches from the Ukraine to the Maghreb, this is not the time for sensible governments to allow lesser domestic threats to distract them from far, far greater international ones.

What we should be seeing from the government, rather than just domestic measures to protect ourselves, is a co-ordinated international strategy to defeat those who threaten us, along with the rest of the civilised world. This should match judicious military action (eg, in protecting the Kurds as a northern bulwark against Isis) with a broader diplomatic effort to first isolate and then defeat the jihadis.

I suspect that in this struggle, diplomacy will play a larger part than military action. This should include the closer engagement of Turkey, a rapprochement with the new reformist government in Tehran, support for moderate Arab states such as Jordan, and strong international pressure on Saudi Arabia and Qatar to stop funding the extremists. And, finally, some action at last to extinguish the burning coal at the heart of the Middle Eastern conflagration – the illegal Israeli settlements on the West Bank which strangle at birth the only peace Israel and the Palestinians can have; one based on a two-state solution.

It is action on this front, far more than on the domestic one, which will keep our country safe.