The reported ousting of Iraqi prime minister Nouri al Maliki is overdue, but the fear is that it has come too late.

The embattled leader has been hanging on to power in the face of calls for him to go, both internationally and latterly in defiance of Iraq's president Fuad Masoum, who has now asked deputy prime minister Haider al Abadi to form a government instead. The damage is already done. Mr Maliki's disastrous period of rule has helped bring about a slide towards civil war through poor leadership and discriminatory treatment of minorities. As a result, alienated Sunni communities are said to have sided with fighters of the Islamic State (IS) as they advanced across the country.

If he does become the new prime minister, Mr Abadi has called for the country to unite against the militants. However, much territory has already been lost and will not be easily ceded. The Obama administration, alarmed at the prospect of a transnational caliphate, is using limited air strikes to try to halt the advances of IS.

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Calls for Prime Minister David Cameron to return from holiday to address the crisis, and for Westminster to be recalled, are premature. Downing Street insists it is currently focused on the humanitarian effort in Iraq, while offering non-military support for US air strikes.

No-one wants to see British armed forces re-engaged in Iraq. But if drops of food aid and other support are not effective in protecting people like the stranded Yazidis, this may change.

The brutality of the treatment of opponents and displaced minorities by IS fighters has been horrific, and the international community cannot stand idly by. The risk of genocide places us under a moral imperative, as former UK armed forces chief Lord Danatt said yesterday.

But there are real issues about the kind of help that is needed. UK forces can support the US efforts with logistical back-up , such as surveillance and refuelling. But weapons are a different matter. As Lord Dannatt also pointed out, there is compelling evidence that IS have come into possession of modern weapons of war formerly gifted to the Iraqi Army.

These fell into their hands as Iraqi army soldiers fled in the face of the Islamic militants' rapid advance. This cannot be allowed to happen again. The exception is perhaps the Kurds in northern Iraq. Convinced they will hold their ground, the US is considering arming them.

Iraq needs a functioning, stable and inclusive government, and it may be that Mr Abadi can produce one. In the short term, however, the UK has a moral duty to prevent genocide and a national interest in preventing the instability that would be caused by the creation of a transnational Islamic state taking in large parts of Iraq and Syria and threatening neighbouring countries such as Jordan.

Putting fighters on the ground is likely to do more harm than good, but a policy of air strikes to establish safe havens has worked to protect Iraqi Kurds in the past. Such a policy does not require the recall of parliament, and could help prevent further atrocities while a longer-term solution is developed.