John Rentoul: The constitution is dead. Would it be so impolite to admit it?

If even the pro-EU Irish won't endorse the Lisbon Treaty, the politicians should throw in the towel

It can take a long time for an idea to die. Especially if it has anything to do with a united Europe. Take the Holy Roman Empire. From 800, when Charlemagne was crowned emperor, it survived for 1,006 years, before Francis II abdicated and dissolved it in 1806. By comparison, the European constitution is a feeble, short-lived thing. It was first mooted about nine years ago as a response to the planned expansion of the European Union to include the former communist countries of central Europe.

Paddy Ashdown, as leader of the Liberal Democrats, was among the first to bring the idea to the House of Commons. In March 1999, he asked Tony Blair what he thought of the idea of "a new constitutional settlement for Europe". Blair replied: "I confess that I am hesitant about trying to draw up a new constitution for the whole of Europe, and the Right Hon Gentleman would find that other countries would also be hesitant." Not hesitant enough, however, and they set up a convention to do just that in 2001. But how right Blair's reluctance proved to be. Not a job for him, after all.

The idea is not clinically dead yet, of course, although it soon will be. It was misconceived from the start. In fact, it began as the dying gasp of an even older idea, that of a federal Europe, which was the treasured project of the bureaucratic elite that created the European Community for the best of reasons after the Second World War. For that elite, the enlargement of the EU, which expanded from 15 members to 25 four years ago, was an excuse to finish their historic task. For the rest of us, this expansion was proof that a new constitution was unnecessary.

It was a tidying-up exercise, British ministers said. A bit of streamlining to make institutions originally designed for six members work effectively. Except that, however effective or ineffective we thought the EU was before enlargement, it didn't seem noticeably different after 1 May 2004. What we got from enlargement was not procedural deadlock. We did not have frustrated ministers and officials spilling onto the streets of Brussels complaining that they were unable to agree on low-energy light bulbs because of the absence of a permanent president of the Council. What we got was half a million Poles to pick our soft fruits and undertake home improvements on a heroic scale.

When the voters of France and the Netherlands threw out the constitution in the summer of 2005, that should have been the end of it. Instead, the corpse sat up in the bath. Blair refused to say that the constitution was dead, out of politeness to "the European idea", the modern-day Holy Roman Empire. Our continental colleagues repaid his compliment by adopting a British approach. Right, they said. What people didn't like about the constitution was that it was a constitution. So they stripped out all the federalist ambitions and kept the tidying-up and the streamlining. A person as president for two-and-a-half year terms instead of a country as presidency for six months, and some changes to Qualified Majority Voting that would have given Britain a bigger share of the vote. (One minister involved told me he had "no idea" why the Poles, who lost out, had agreed to it, "but they had".)

It was all pointless, however, because enlargement had already happened and directives on low-energy light bulbs were still being happily agreed.

Contrary to the conspiracy theories of the anti-European obsessives, most European citizens – including most Britons – accepted that the reforms of the Lisbon Treaty did not amount to a constitution. Last August the Daily Mail inexplicably failed to put a shocking opinion poll finding on its front page. It asked, "From what you have seen or heard, do you think the new treaty does or does not represent a constitution for the European Union?" Nearly half, 44 per cent, said it did not, and the 24 per cent who thought it did were out-numbered by the don't knows (or possibly don't cares).

Yet the simple fact that the Lisbon Treaty was not a constitution was no incentive to vote for it. The top reason given for voting "No" in Ireland, by 30 per cent in an Irish Times poll, was: "I don't know what I'm voting for/I don't understand it." Some of the reporting of the referendum hinted that this reflects badly on the Irish. On the contrary, it is entirely rational. If the advocates of the Lisbon Treaty have been unable to explain its benefits – if they have been unable to make a simple case for it to one of the most pro-European electorates in the Union – it did not deserve to pass.

That was the fatal flaw from the start. The constitution was not conceived as a document capable of winning the support of the peoples of Europe in referendums. Now that the constitutional idea has failed the democratic test, despite being watered down, and despite its testers being an electorate that has benefited so greatly from EU membership, it really is all over. Which is why the response of Gordon Brown and David Miliband is so curious. I understand the need for Blair's tact three years ago, but why have Brown and Miliband insisted that they will continue with British ratification?

I mention them separately because their calculations are slightly different. They both have to go to Brussels this Thursday, but it is Brown who takes the lead, and he may not want to offend his fellow leaders by telling them that their pet scheme cannot be resuscitated this time. But Miliband has a different audience, that of Labour MPs at Westminster, whose talk is all of candidates and leadership campaigns. One former minister even told me that the lesson of David Davis's resignation was: "At least it shows that one member of the shadow cabinet has the guts to defy the leader." They are watching Miliband's every television appearance for evidence of prime ministerial potential. Our poll today is agonisingly ambiguous for them, because it suggests that, although 40-41 per cent think that Miliband or Alan Johnson would be better than Brown as prime minister, a larger proportion disagree.

So Miliband's decision to reinforce people's perception of him as out of touch was inexplicable. He chose to go on television to say: "I think it is right that we follow the view that each country must see the ratification process to a conclusion." Wrong answer. Big mistake. The Holy Roman Emperor has no clothes.