For the third time in a decade, Britain is engaged in a major military action in a Muslim-majority country. David Cameron and his allies have resurrected the doctrine of liberal interventionism, which had been poisoned by the disastrous invasion of Iraq, to justify the use of force in Libya. The notion of a "responsibility to protect", born of the genocides in Rwanda and Bosnia in the mid-1990s, is one that justly retains political support. It was right to intervene in Kosovo in 1999 to halt Slobodan Milosevic's murderous drive for a "Greater Serbia" and it was right to intervene in Sierra Leone in 2000 to defend that country's democratically elected government from the nihilistic Revolutionary United Front.

To his credit, Mr Cameron ensured that there was a clear legal basis for military action in Libya by securing author­isation from the United Nations. The rapid assembly of an international coalition to enforce UN Resolution 1973 was a diplomatic triumph. But, in the days since, it has become increasingly clear that there is little worldwide agreement on the intervention. It is hardly surprising that China and Russia, committed as they are to an outmoded concept of state sovereignty, have condemned the action. But those opposed to the intervention also include India, Brazil, Germany and the African Union. The lack of an international consensus reflects a justified scepticism about the merits of military action.

The tension between the formal aim of civilian protection and the underlying desire for regime change has led to an alarming split between the UK government and our armed forces. The hawkish Defence Secretary, Liam Fox, with the apparent support of Downing Street, declared that Muammar al-Gaddafi was a "legitimate target" but the chief of the defence staff, General Sir David Richards, insisted that this was "absolutely not" the case. Such confusion reflects a wider uncertainty over the ultimate aim and purpose of the mission.

Mr Cameron has repeatedly stated that it is up to the Libyan people to "determine their future", and quite so. But this avoids the question of what will happen if the air strikes result not, as hoped, in the fall of Colonel Gaddafi, but in a military stalemate. Will the coalition seek authorisation for the deployment of ground troops, or will it agree to police an indefinite no-fly zone (NFZ)? The NFZ established in Iraq to safeguard the Kurds in the north and the Marsh Arabs in the south lasted for 12 years. The allies' pledge to protect civilian life in Libya could yet entail a similar commitment.

Perhaps most troubling is the lack of attention the coalition has devoted to those forces it is now supporting against Colonel Gaddafi. The Senoussi, whose king was deposed by the colonel in the military coup of 1969, remain the most powerful opposition group. But their allegiance is primarily to a clan-based society, certainly not to secular liberal democracy. The coalition's intervention could lead to the de facto partition of the country or, worse, a protracted civil war. The allies have yet to indicate how they will respond if and when the opposition gains the upper hand. It is far from clear how a commitment to protect civilian life operates in a situation in which Colonel Gaddafi's supporters are on the defensive.

The west's decision to intervene in Libya rather than in, say, Yemen, where state forces shot dead 52 unarmed protesters on 18 March, or in Bahrain, where the ruling Khalifa family, aided by the Saudi autocracy, has brutally suppressed the democratic uprising, leaves it open to the charge of double standards. That the UK and the US refuse, even now, to stop arming and supporting these despotic regimes explains why so few in the region are prepared to view the military action in Libya as a "moral" gesture.

Because of Britain's sorry history of military intervention in the Arab and Muslim world, the government has a heightened responsibility to the people of the region. Mr Cameron has promised a limited campaign in Libya but the coalition's ad hoc approach does not inspire confidence. Until there is far greater clarity on the scope and ambition of the mission, the fear remains that it will do more harm than good.