The Yes campaign may be leaderless but it can still win the referendum on Europe

Europe is back. The issue that has a unique capacity to wreck British governments and split political parties is about to cause unpredictable havoc once more. This week the precise question to be posed, in a referendum on the European constitution, has been leaked. The No campaign was already up and running, confident of an historic victory. Meanwhile, there are signs of tactical divisions at the top of the government over how to make the pro-European case in the run up to a referendum.

Europe is back. The issue that has a unique capacity to wreck British governments and split political parties is about to cause unpredictable havoc once more. This week the precise question to be posed, in a referendum on the European constitution, has been leaked. The No campaign was already up and running, confident of an historic victory. Meanwhile, there are signs of tactical divisions at the top of the government over how to make the pro-European case in the run up to a referendum.

Indeed, here is an early example of the bizarre chaos the issue of Europe is capable of causing. Although the Yes campaign lacks leadership, its leaders already appear to be split. Peter Mandelson warns about the dangers of gloating over the British economy. Gordon Brown points out that sometimes even Michael Howard gloats about economic successes in Britain. Mr Mandelson seeks a greater emphasis on the positive elements of Europe. Mr Brown highlights British successes and the need the Europe to embrace more extensive reform.

On the surface at least, pro-Europeans have cause to be depressed. The polls are bleak. There is no clear leadership. There is also no escape. Increasingly it is the view in ministerial circles that a referendum will take place in Britain. Senior ministers predict that, in the referendums being held elsewhere in Europe, there will be a succession of "yes" votes. The Europe Minister, Denis Macshane, points out that quite often in Britain there is an assumption that controversial European initiatives will not be implemented. Nearly always the policies are in place on schedule. He is one of those who believes no other country will veto the constitution before Britain decides.

Seeking any possible advantage, there were some brief ministerial discussions about the nature of the question to be posed in the referendum. One or two ministers suggested that there should be a reference to the parliamentary approval of the constitution, necessary before the referendum can take place, in order at least to convey a more positive tone. Very quickly it was decided that the question should be straightforward and neutral. In around 18 months time British voters will be answering the question: "Should the United Kingdom approve the treaty establishing a Constitution for the European Union?"

At the moment the response would be a loud "no". Yet that could easily change in the next 18 months. The occasional public spat between Mr Brown and Mr Mandelson does not reflect a fatal divide at the top of the government over the referendum. Mr Brown will play a high-profile role in the campaign, almost certainly as Chancellor. Indeed one of the reasons I do not believe Mr Blair will move him after the election is the influential role he could play in the referendum. It would be impossible for Mr Brown to hide for the duration of the campaign or the months preceding it even if he wished to do so. Jack Straw, regarded as another sceptical minister, will also be out there campaigning. Indeed he is already out there. Earlier this week he delivered a weighty speech to the Centre For European Reform warning in considerable detail about the dangers of rejecting the constitution.

Senior ministers have finally realised the issue cannot be ignored until the election is safely out of the way. Almost certainly the bill that gives the go-ahead for a referendum will be debated in the Commons next month. This will be one of the few occasions when a parliamentary event attracts wider interest. The government's familiar position will come under scrutiny, but the Conservatives will have questions to answer as well. Michael Howard has still to explain how a Conservative government would successfully reject the Constitution and renegotiate existing EU treaties without the support of any other countries.

In timing and in tone, the referendum on the constitution is beginning to look increasingly similar to the one that took place in 1975 on Britain's continuing membership. In October 1974 Harold Wilson fought an election campaign promising a referendum, but without Europe being a dominating theme. By June 1975 he was able to win a referendum.The Yes campaign stood reassuringly for the status quo as Britain was already a member of the common market. A "no" vote was seen as the more unpredictable break with the status quo.

The same argument applies in the context of the European Constitution, only more so: if there is a "no" vote Britain would be going it alone while causing chaos in the rest of Europe. This factor alone may influence some of the more thoughtful Euro-sceptics to vote "yes". To take one example, the former Foreign Secretary, Dr David Owen, disapproves of the constitution and plans to vote against. In a recent interview he told me he would hesitate in doing so if there had been a series of decisive "yes" votes elsewhere leaving Britain as the country responsible for leaving the EU in near terminal anarchy.

Those already campaigning for a "no" vote cannot agree on the consequences of such chaos. At least the United Kingdom Independence Party argue openly and logically that a "no" vote would result in Britain leaving the European Union. Others argue, with more perversity, that a rejection of the constitution would leave Britain in a stronger position within the European Union. Here is an ideological split that will lead inevitably to a confused and incoherent message from the No campaign.

The government plans to use its presidency of the EU in the second half of next year to put the case for Europe and the dangers of withdrawal. Some pro-Europeans want a formal campaign to start now and seek a more evangelical message about the virtues of Europe. Such an approach might work in a country at ease with Europe but in Britain pragmatic stealth is likely to produce more practical results, as it did when Harold Wilson waved his political wand in 1975.

In many ways it is odd that a conjuror's wand is required once more. During the heated debates in the House of Commons in the early 1990s over the Maastricht Treaty, Conservative MPs put forward their alternative vision of a less integrationist, enlarged EU. At a time when their vision has been realised they contrive to be in an even greater fury and look with increasing passion towards a new relationship with the United States. But senior pro-Europeans tell me that the Bush administration is viewing the possibility of a "no" vote in Britain with some alarm. President Bush could yet repay his old Prime Ministerial friend by making clear that Britain is best placed to form a relationship with the US as a leading member of the EU. What a twist: "Bush swings Europe referendum for Blair".

If there is a "no" vote, Europe's latest contribution to the remaking of British politics would be the near destruction of new Labour and the Liberal Democrats. Against the odds, I regard it as more likely that the Conservative party will be forced to change, to its own long term benefit, in the light of a convincing Yes victory.

s.richards@independent.co.uk