Earlier this week, in his inaugural speech to the UN General Assembly, David Cameron enthused about the change of power in Libya and made a plea for the United Nations to be united not just in condemnation of repressive regimes, but in action.

By yesterday, however, what had been hailed by some as a claim to leadership that was almost Blairite – for better and worse – in its ambition seemed like ancient history. Mr Cameron was on his way home, and British diplomacy was meeting its first challenge of the new UN year in a position that might, to borrow a phrase used to describe the US stance on Libya, be termed leading from behind. The Government was mired in a quandary it had hoped against hope would never arise.

In his keenly awaited speech to the General Assembly, the President of the Palestinian Authority, Mahmoud Abbas, announced that he had just made a formal application to the Security Council for Palestine to be admitted to the UN as a full member. He was followed at the General Assembly podium by Israel's Prime Minister, Benjamin Netanyahu, who lost no time in rejecting the claim for UN recognition out of hand.

This was precisely the stand-off that Britain, the United States and others had done their utmost to avoid. The US had invested much time and effort in trying to dissuade Mr Abbas from submitting his application. That it failed was hardly surprising, given that the only arguments advanced, in public at least, were that no UN resolution could substitute for agreement with Israel, and that a pre-emptive bid for recognition risked scuppering Middle East talks. With Mr Neta-nyahu's fragile coalition in no mood to negotiate and all talks long moribund, this hardly left the Palestinians a great deal to lose.

As much as the international coalition that helped to protect the uprising in Libya can be deemed a success – with the important caveat that Muammar Gaddafi has not been apprehended – the Western diplomacy that tried to forestall yesterday's Palestinian application for UN recognition is an abject failure. It is a failure in practice, both because the US may now have to resort to its veto to fend off recognition – the very option it had wanted to avoid – and because Britain has been forced to choose yet again between Europe and the US, and looks set, awkwardly, to abstain. It reportedly rejected a French compromise plan that would have seen Palestine granted the same non-member status as the Vatican.

But the failure is also moral – on the part of Britain, as much, if not more than, any other power. As the Mandate power in Palestine for 25 years, Britain had an obligation to create and foster self-governing institutions. It left without doing so. More than half a century later, supporting the Palestinians' aspiration to statehood at the UN is the very least Britain should do.

Venting his frustration, the late Israeli statesman Abba Eban once said of Palestinian leaders that they never missed an opportunity to miss an opportunity. The same cannot be said of Mahmoud Abbas, who seized the moment yesterday and threw down a gauntlet to world leaders in New York. In not supporting UN membership for Palestine, if that is what the British Government decides, it is we – to our shame – who will be reproached for missing this historic opportunity now.