When Richard Goldstone, the judge who headed a UN fact-finding mission to Gaza, partially recanted last month – an act that was disowned by fellow members of the mission – the saga was used as Exhibit A in the case against the UN. The organisation, it was claimed, was so inherently biased against Israel that it lacked the moral authority to investigate it. Where was the Goldstone report about Sri Lanka, some asked?

A UN panel has just produced such a report about the carnage of civilians which took place two years ago when government forces crushed the Tamil Tigers. It is as hard-hitting as anything Goldstone produced, and therefore is just as likely to be shelved. The point is that truth and accountability, let alone international justice, are not divisible. One country's ability to bury the evidence of war crimes endangers how civilians are treated in all other conflicts. A single failure of international justice is also a collective one.

That there is credible evidence that government soldiers targeted civilians, shelled hospitals and attacked aid workers in the final months of the war against the Tamil Tigers is indisputable. That the Tigers used civilians as human shields and shot those attempting to flee the carnage at point-blank range is equally true. Tens of thousands died as a result of these twin brutalities. The zone that the government established in the north-east of the country in the final months of its civil war was an area where savagery was organised on a daily basis. Civilians queueing at a food distribution centre would be shelled while President Mahinda Rajapaksa's office instructed the army to stop what it claimed it had not been doing. It was a no-journalist, no-aid-worker zone, but it was anything but a no-fire zone.

Two years on, the goal has to be to establish an independent inquiry into these events. The Sri Lankan government has consistently opposed the UN, and at one point organised demonstrations against UN staff in Colombo. It has established two ad hoc bodies, but no one has been held accountable. Its supporters claim that anything more trenchant would endanger the peace that has reigned on the island since. All of these arguments are self-serving.

That leaves the UN itself. The secretary general, Ban Ki-moon, claims he lacks the authority to order an inquiry into the mass killings without the consent of the Sri Lankan government, which is not a member of the international criminal court, or a decision by an appropriate international forum of member states. Human Rights Watch is right to disagree. Having fought to establish the panel, the UN secretary general has a responsibility to finish what he started.