GIVE them credit for persistence and ingenuity. The “bomb Syria” bloc in the British Establishment isn’t taking “no” for an answer.

In 2013 they were urging war against the Syrian government over its alleged use of chemical weapons. The House of Commons defeated David Cameron’s proposal in what was a landmark vote for anti-war sentiment in this country.

Indeed, it stopped Barack Obama’s own plans for attacking Syria in their tracks and represented a decisive democratic rupture in the Anglo-US war front in the Middle East.

Imperial interventionists in both major parties have been smarting ever since. The rise of Islamic State (Isis) to control much of Syria’s territory — a consequence of the civil war fostered by the Western powers, among others — seemed to offer another excuse for intervention.

After all, British bombers are already participating in the US-led attack on Isis in neighbouring Iraq — the latest military intervention in that country, and one having no better outcomes than all the previous interventions.

It is now pretty obvious that bombing by Western powers is not going to push back Isis. That could only be done by the forces of strong and sovereign states in Iraq and Syria, able to mobilise support from all sections of the people.

Western policy has actually been directed towards obstructing that development, through the sponsorship of sectarian strife across the Middle East and the destruction of one state after another in the region.

Now the next reason has been dredged up — that old stand-by of “humanitarian” intervention. Labour MP Jo Cox has joined forces with Tory Andrew Mitchell to advocate military action… to save civilian lives.

They wrote in The Observer: “We need a military component that protects civilians as a necessary prerequisite to any future UN or internationally provided safe havens. The creation of safe havens inside Syria would eventually offer sanctuary from both the actions of [Bashar al-] Assad and Isis, as we cannot focus on Isis without an equal focus on Assad. They would save lives, reduce radicalisation and help to slow down the refugee exodus.

“The approach of focusing on civilian protection will also make a political solution more likely. Preventing the regime from killing civilians, and signalling intent to Russia, is far more likely to compel the regime to the negotiating table than anything currently being done or mooted.”

Of course, if humanitarianism was really a consideration, Britain would have stopped funding and arming the Syrian civil war some time ago. It would be welcoming far more refugees from the conflict it has fuelled.

But let us take the appeal at face value for a moment. How could it be implemented? Our bipartisan armchair strategists are obviously riled by Russia’s escalating military involvement in Syria. But it is a fact. What form of military intervention could now be undertaken which would not lead to a clash with Russia, they do not say. Even the head of MI6 has acknowledged that “no-fly zones” are no longer a possibility, unless the Nato powers are prepared to countenance conflict with Moscow.

The reality of no-fly zones and safe havens, benign as they sound, is regime change. That is the clear aim of the proposal. The Assad government’s forces — or those supporting it — would be the target.

A no-fly zone would represent no challenge to Isis whatsoever. The caliphate lacks an air force.

If anyone still doubts that regime change is the real agenda, let them cast their minds back to the Libyan war. That began with Cameron and then French president Nicolas Sarkozy pushing the United Nations to endorse just such a no-fly zone, ostensibly to protect the people of Benghazi from a massacre that Libyan ruler Gadaffi was then allegedly contemplating.

Enforcing the zone quickly morphed into bombing Libyan government troops in co-ordination with the anti-Gadaffi rebels on the ground. The result was the swift transition of “humanitarian intervention” into regime change, with results that are all too clear today. A ruined and divided country, a shattered society and hundreds of thousands of refugees risking life and limb to cross the Mediterranean to Europe.

In Syria today, the winners from a war to set up safe havens — an operation which would also require the deployment of ground troops into Syria — would most likely be Isis. It would be best placed to expand into many of the areas cleared of regime forces.

Such plans fuel the fantasies of neoconservatives on both sides of the Atlantic who dream of creating a “third force” capable to taking over Syria in opposition both to Assad and to Isis.

Obama’s efforts to create a militia to carry out such a plan have ended in fiasco. No more than five such fighters are still in the field. So they are left with the non-Isis rebel groups in Syria. These include the Free Syrian Army and the local al-Qaida affiliate, trading as the Nusra Front.

These groups are drawing support from a range of foreign powers, including the US, Turkey, Saudi Arabia and other reactionary Gulf states. The Assad government is actively supported by Russia and Iran.

The clear need is not for Britain to jump further into this toxic mix. It is for a negotiated diplomatic end to the dreadful civil war which has laid waste to Syria. Ultimately, only the Syrian people can determine their own future political arrangements.

But the foreign powers could assist by all ending their military interventions — both open and clandestine — in Syria, ending the bombing and the arming of one side or another.

They should further promote peace by abandoning all the preconditions laid down for negotiations. Such preconditions only serve to prolong the conflict and to give either government or opposition hope that foreign military and diplomatic support could somehow lead to all-out victory.

Peace and the reconstruction of Syrian society is obviously the only long-term solution to the refugee crisis there as well.

Cameron, however, wants Britain to pile into the war, adding bombing of somebody or other to the existing levels of covert interference.

No doubt he is in part animated by a wish to be seen to be “doing something” that keeps Britain a key player in Middle East politics.

But mostly he just seems to want to reverse the humiliation of autumn 2013, when he became the first British prime minister to lose a vote in Parliament on going to war.

He has so far hesitated to bring a definite proposal forward for fear of a repetition. Many influential Conservative backbenchers can see no rational case for war.

He draws strength, however, from signs of support for bombing in the Labour ranks. The parliamentary arithmetic is still more unfavourable for peace than it was two years ago. But a united and resolute Labour position against bombing would most likely still stay his hand.

That is why the arguments within Labour’s ranks on this issue today are of first-rate importance.

• Andrew Murray is chair of the Stop the War Coalition.