No one has a clue what to do after war. Now that really is frightening

A few days ago there was an alarming debate in the House of Commons. The exchanges were barely reported, yet if they had taken place on Radio 4's Today programme or Breakfast with Frost they would have made screaming front- page headlines the following day.

The debate was about the whopping great question that continues to be largely overlooked in the build-up to war with Iraq. Even the otherwise excellent Newsnight with Tony Blair on Thursday failed to cover it. The issue that just a few MPs were addressing in the Commons was this: what the heck happens to Iraq and the surrounding region after the war? The main speaker was the International Development Secretary, Clare Short.

The debate was alarming for several reasons, but the main one was that she did not seem to have any clear answer to the question. What makes this even more disturbing is that Ms Short, normally makes it her business to crusade about the responsibilities of the international community in the aftermath of war. In this debate she was short on detail and, uncharacteristically, resorted to personal attacks against various Tory MPs who were making perfectly valid points. She even threw a dart or two at her opposite number, Caroline Spelman, who is the closest the Conservatives come to sainthood on their front bench.

After the extraordinary debate, one or two of the Tories wondered privately whether this was a sign that she was on the verge of resignation, that she had given up. This was not my interpretation of Ms Short's contribution. Indeed, she provided, for the first time, a justification for war. She said that a conflict might be necessary in order to protect the authority of the UN, adding: "We should consider taking military action if it is necessary to minimise suffering and to maximise the speed with which Iraq is reconstituted."

Presumably this slightly convoluted justification will be her defence for staying in the Cabinet when the war starts. But evidently she is far from convinced about the case for war, not least because of the possible humanitarian consequences. At one point in the debate she warned of a "humanitarian nightmare". That was one of the quotes that would have made it on to the front pages if she had uttered the words in a studio rather than in the privacy of the Commons. She has said it before, but as we move closer to war, the more potent her warning becomes. She spoke specifically of the dangers arising from violent conflicts between different ethnic groups within Iraq, and from bombs that could damage electricity and water supplies in a country with an already decaying infrastructure, and where a third of the population in the centre and south of the country suffer from what she described as "chronic malnutrition".

It was at this point that various Tories pressed her about what was being planned to alleviate or prevent these potential horrors. A summary of Ms Short's response was "Not a lot". More revealingly, she explained why nothing much was being done. She told MPs that neighbouring countries did not want to talk to each other – or to more distant countries – about what they might do for humanitarian purposes in the event of war. This was largely because they were opposed to a military attack and hoped that one could still be avoided. More widely, according to Ms Short, the UN has been cautious about making arrangements for the aftermath because "It did not want to say to the world that the UN is preparing for war... because of seething anxiety about a possible conflict across the international system".

Ominously, it seems that the "seething anxiety" about a possible war is hampering negotiations about co-ordinating the international response when it is over, thereby making the consequences of conflict even more dangerous.

Ms Short is not alone in her uncertainty. Yesterday the chairman of the Foreign Affairs Committee, Donald Anderson, told me on Radio 4's Week in Westminster that he was "not sure" about the plans for Iraq beyond the recognition of an immediate need to maintain law and order. Maintaining law and order might be easier said than done. So far, the only concrete proposals are for a few British troops to remain in the region after any conflict. Mr Anderson is an authoritative supporter of war if it is backed by the UN. He is rarely off the airwaves exploring the possible permutations in the build-up to war. But even he is unsure about what would follow it.

Ms Short's evasiveness is more revealing. After the Afghanistan conflict she urged world leaders not to turn away. Following a visit to the country early last autumn she expressed alarm at the growing signs of disorder outside Kabul and the apparent indifference of the international community, especially the US. As part of her on-going dialogue with Mr Blair about the possible war against Iraq she has pressed him relentlessly about the importance of not forgetting Afghanistan. To his credit, he has not forgotten. But now in the face of a potentially bigger humanitarian crisis Ms Short cannot say very much – or does not have very much to say.

This week much of the focus in Britain will be on the possibility of a second UN resolution and the potentially precarious position of the Prime Minister. There is a highly charged drama being played out here, but with a fairly predictable denouement. Next Friday the senior UN inspector, Hans Blix, will report back to the UN, almost certainly demonstrating in some form or other that Saddam is not fully co-operating. My understanding is that Mr Blix in his meeting with Mr Blair on Thursday indicated that he was far from confident that Saddam would switch from devious obstruction to complete co-operation. Soon after the Blix report it is more likely than not that there will be a second UN resolution, and most Labour MPs, along with the entire Cabinet, will fall in line. If Mr Blair fails to get the second resolution, he faces a political nightmare, but my hunch is that he will get it. The UN has become the blanket that will protect all those MPs who continue to have great private doubts about the war.

But there are questions about the future of Iraq and the neighbouring region that extend well beyond whether or not Presidents Chirac and Putin put their names to a deftly worded UN resolution. Mr Blair would enhance his case for war considerably if he could outline what is envisaged afterwards. He must know that such information would address some of the "seething anxiety" whirling around Britain. Presumably there is a simple reason for the whopping gap in the debate. The Prime Minister does not have the information to give.