Last night the Commons voted against Britain taking military action – by accident. It may be an outcome supported by a majority of the public, but it was not what any of the main parties or their leaders wanted.

David Cameron, in an act of terrible miscalculation, tried to bounce MPs into supporting military action in principle before they or the country were ready. Ed Miliband – who was very clear he did not rule out supporting action – felt the evidence – not least that from the UN weapons inspectors due in the next two days – should come before the decision.

If Cameron had supported Labour’s sensible and measured amendment or waited until next week, the vote would have gone through. Instead, both leaders seem now to have ruled out supporting military action, regardless of what the weapons inspectors say and Presidents Obama, Hollande and others decide to do.

This is an extraordinary moment for British Foreign policy and, I’m inclined to agree with the former Lib Dem MP, Paddy Ashdown, a worrying one. Britain has said dictators can use chemical weapons, killing thousands, and we will do nothing.

Cameron and the Government did precious little to prepare the public or MPs for this week’s rush to decision. But, public opinion is fickle. More reports like last night’s on the BBC of an appalling attack on a Syrian primary school could quickly change the public mood.

I voted for Labour’s amendment (below) because it mapped out a sensible process for making a decision. I abstained on the Government’s motion because I felt Britain should keep our options open. Both those approaches now appear closed. It is now left to France, America and others to uphold international law, human decency and the principle of humanitarian intervention.

Labour’s Amendment

This house expresses its revulsion at the killing of hundreds of civilians in Ghutah, Syria on 21 August 2013; believes that this was a moral outrage; recalls the importance of upholding the worldwide prohibition on the use of chemical weapons; makes clear that the use of chemical weapons is a grave breach of international law; agrees with the UN Secretary General that the UN weapons inspectors must be able to report to the UN Security Council and that the Security Council must live up to its responsibilities to protect civilians; supports steps to provide humanitarian protection to the people of Syria but will only support military action involving UK forces if and when the following conditions have been met that:

(a) the UN weapons inspectors, upon the conclusion of their mission in the Eastern Ghutah, are given the necessary opportunity to make a report to the Security Council on the evidence and their findings, and confirmation by them that chemical weapons have been used in Syria;

(b) compelling evidence is produced that the Syrian regime was responsible for the use of these weapons;

(c) the UN Security Council has considered and voted on this matter in the light of the reports of the weapons inspectors and the evidence submitted;

(d) there is a clear legal basis in international law for taking collective military action to protect the Syrian people on humanitarian grounds;

(e) such action must have regard to the potential consequences in the region, and must therefore be legal, proportionate, time-limited and have precise and achievable objectives designed to deter the future use of prohibited chemical weapons in Syria; and

(f) the Prime Minister reports further to the House on the achievement of these conditions so that the House can vote on UK participation in such action, and that any such vote should relate solely to efforts to deter the use of chemical weapons and does not sanction any wider action in Syria.