The witch-hunt against Kofi Annan and the United Nations over the Iraq oil-for-food scandal is, quite simply, a scandal all on its own. The leaders of this lynch mob in the US Congress and the rightwing commentariat are not gunning for Mr Annan so much as aiming to destroy the UN as an institution. That would be a disaster - for all of us, including, especially, the US.

It is hard to know whether those conducting this campaign are being deliberately mendacious, or whether they cannot add up or understand which bits of what institutions policed the sanctions against Saddam Hussein.

True, the oil-for-food regime presented genuine moral dilemmas about unpleasant policy alternatives in dealing with the Iraqi dictatorship. Furthermore, any sanctions policy against any country offers rich pickings to those with the skills to circumvent it. But let us look at the facts.

First, the oil-for-food policy was devised and run by the member states of the UN Security Council, not by the UN Secretariat. All of the roughly 36,000 contracts were approved by a Security Council committee dominated by the US and the UK. Of these, about 5,000 were held up. But objections were entirely about imports to Iraq that might have offered Baghdad dual-use technology with which to reconstitute its weapons programmes. There was not one objection about oil-pricing scams, although UN officials brought these to the attention of the committee on no fewer than 70 occasions.

Second, the "headline" figure touted by a Senate sub-committee of a $21bn (£11bn) leakage from the scheme - transmogrified by editorialists into "US taxpayers' dollars" - is fantasy, albeit a damaging one. This covers smuggled oil and, even though oil-for-food only started in 1996, Iraqi shipments to Jordan and Turkey from 1991 sanctioned by waivers voted by Congress.

Forgotten in this intellectually dishonest campaign is the fact that sanctions worked: Iraq had no weapons of mass destruction. And that oil-for-food mitigated their effect on the Iraqi people: malnutrition was halved, whereas since last year's invasion of Iraq it has almost doubled.

If the independent inquiry headed by Paul Volcker, the former Federal Reserve chairman, finds any UN official complicit in Iraq's roughly $4.4bn oil price skimming, then that person should have his diplomatic immunity lifted and be prosecuted. But there is nothing here to be laid at the door of Mr Annan, even though the lobbying activities of his son Kojo, who was still receiving severance payments from a company seeking Iraq's trade after oil-for-food started, will have hurt him.

President George W. Bush should also reflect on just how much the US needs the UN, not just in Iraq but in dealing with potential crises such as Iran, and on just how much more dysfunctional the world could become if the UN went the way of the League of Nations between the two world wars. We know that that way lies chaos.