To creep or not to creep, that is the question. Britain's Libyan war is entering its most dangerous phase. The great lie has once again been rumbled, that air power can deliver any sort of victory. The humanitarian imperative is in full cry, swamping the media and blinding strategy with daily tales of horror from the front. The mission, confused from the start, is moving where such missions always move, towards ever deeper engagement. Why does no one see it?

The prime minister, David Cameron, faces daily accusations of halfheartedness and desertion from his new comrades in arms, the Libyan rebels. In reply he complains of UN "restrictions" on his freedom to "take all necessary measures … to stop Gaddafi murdering people in Misrata". His minister for mission creep, Andrew Mitchell, has been in New York waving the shrouds of dead Libyans before the security council and demanding changes in the rules of engagement. The foreign secretary, William Hague, offers the rebels "non-lethal assistance", which appears to mean flak jackets and 10 training officers to offer "logistics and intelligence", but not to fight. This is war through the looking glass, glory sought from the blood of others.

There can be no argument that ghastly things are happening in the streets of Misrata, the provinces of Syria, the towns of Yemen, the hospitals of Bahrain and the streets of Baghdad. Liberal intervention has never had much truck with Kant and universalism. Bombs do not follow ethics, they follow cameras. If it bleeds it leads. Libya is today's war, and that is that.

Cameron watchers are mesmerised by how he found himself up this creek with no paddle other than the dubious Nicolas Sarkozy. The iron law of Nato, which is do nothing unless the Americans are in the lead, was clearly breached. Barack Obama could not have been clearer in not wanting a new Middle East conflict.

The PM is said to be eager to imitate Tony Blair and hang a dictator's scalp on his belt. But even Blair understood that this required a readiness to use main force, which he did in Kosovo without any nonsense about UN resolutions. Cameron helped draft UN resolution 1973 that denied him any such scope. This won him Arab support, but that has proved predictably fickle, and may turn counterproductive as the war drags on.

The resolution is rotten, based on the false premise that a no-fly zone can determine a civil war. It has forced Cameron into such semantic contortions as declaring that "to leave Gaddafi in power would be an unconscionable betrayal", while denying "regime change". He tries to kill Gaddafi by bombing his compound and asserts that "he must go", yet denies any intention to pursue "all necessary measures" to get rid of him, such as invading and occupying Libya. He cannot even arm the rebels. Did Downing Street not spot the trap, that the resolution was drafted to fail? If ever a British military adventure was "victory-lite", Libya 2011 is it.

If I were a Libyan rebel I would be furious. As a mere British citizen and taxpayer I only wonder what game is being played in north Africa in my name and with my money. How can Cameron say he is short of cash when he can blow £500,000 destroying one tank? Britain is using bombers not to support invasion but as an alternative to invasion. This strengthens sympathy for the bombed, not least because bombs constantly miss their targets. Nato, which presumably means the RAF, has already killed civilians in Sirte and blasted a rebel force it was supposedly protecting, despite denying it was acting as "a rebel air arm".

The commitment of the Arab League to the venture has predictably evaporated. An article justifying the intervention, signed last week by Cameron, Sarkozy and Obama, was conspicuously not signed by the Arab League's Amr Moussa, who backed the bombing just a month ago. Libya's neighbours, Egypt and Tunisia, have not taken part in any military operation or even lent airbases.

Al-Qaida hovers over the Maghreb, awaiting more pickings from western ineptitude. It must be overjoyed that the two powers still with a stomach for the Libyan fight are the region's past imperialists, Britain and France. The prospect of a western puppet regime in Tripoli – being planned, we assume, by the post-Chilcot Foreign Office – must answer every jihadist prayer.

Both the coalition and the Labour frontbenches are beating the drums of war. None of them reads history. Cameron's bedtime book should be the Eden-Eisenhower correspondence during Suez, when the latter pleaded for Eden to stay out of this theatre and recognise how attacking one Arab forced all others to side with him. America, said Eisenhower, would have no part in an invasion. Eden ignored him and paid the price.

Most members of Nato and the EU are absent from the Libyan imbroglio. This is not, as the western media incant, because they are wimpish, small-minded and, as the New York Times grandly puts it, parochial. It is because they are not stupid. They can see no point in repeating what happened in Belgrade in 1999 and Baghdad in 2003, when hundred of millions of dollars were spent dropping ordnance, in a destruction mendaciously said to forestall the need for ground troops.

Throughout the west there is a desire to relieve people in distress, but when humanitarians arrive with screaming missiles and a clear political agenda, those being attacked are understandably suspicious of motive. I do not believe Cameron is after Gaddafi's oil, but tell Tripoli's residents, whose sufferings were happily ignored by British governments when their leader seemed secure. The first humanitarian duty to those who are suffering should be to relieve that suffering, not to fight their civil wars, suppress their dictators, partition their countries and destroy their infrastructure. Something has polluted foreign policy.

Cameron wrote last week that he was bombing Libya to ensure that "it will be the people of Libya … who write the next chapter in their history". Why, then, is he trying to write it? For all the silly talk about level playing fields, Britain is helping to prolong the agony of another country's civil war. Cameron may get lucky and someone may shoot his fox. But at present the only way out of this mess is to withdraw and leave it to the diplomats. The toughest decision for any commander, said Wellington, is "to know when to retreat, and to dare to do it". Does Cameron dare?