Yet, in spite of the importance of the referendum result, the government and its allies in the Liberal Democrats and the Conservative party have kept their heads well down. It is legitimate for the government to argue that the referendum should be delayed until after the next general election, given that the election is likely to take place in the early summer of 2005. But a conspiracy of silence by the pro-Europeans can only play into the hands of opponents. Supporters need to act now.

The first detailed survey of public opinion since the referendum was announced, carried out by Mori for the Foreign Policy Centre and published today*, shows that the anti-constitution camp is well ahead. The Mori poll found only 31 per cent in favour of the UK adopting the constitutional treaty. However, it demonstrates that, contrary to the pessimism of many commentators, the Yes camp could win.

The key finding of the survey is the public uncertainty. Only 35 per cent have made up their minds. A large chunk of the electorate could shift their position, according to their view of whether a European constitution was good or bad for the UK. If one adds these “waverers” to those already in favour, they make up 54 per cent of the voters. In addition, a significant number, about one-fifth, are “don’t knows”. So there is everything to play for.

But if the Yes camp is to exploit the fluidity of opinion, it needs to seize the initiative. Crucial for a Yes result will be a well planned, powerfully sustained campaign. To a considerable extent, the No camp can afford to rest on their laurels. The pro-constitutionalists must start making up ground early.

The campaign will have to be broad-based and able to appeal across party lines. The Mori survey shows conclusively that neither Tony Blair nor the Labour party can win the vote on their own. Of course, it will be necessary to mobilise the support of Labour voters who are now split narrowly against adopting the constitution. Fortunately, most of the Labour opponents are “waverers”, who are likely to be persuaded by a Labour cabinet campaign that must be spearheaded by Gordon Brown, the chancellor, John Prescott, deputy prime minister, and Jack Straw, foreign secretary, as well as Mr Blair. But if vital Liberal and Tory “waverers” are to be won over, the Yes campaign will also need the active support of Charles Kennedy, leader of the Liberal Democrats, and pro-European Tories such as Kenneth Clarke, Michael Heseltine and Christopher Patten.

The Yes campaign will need to be conducted at different levels to succeed. In spite of the barrage of propaganda in the Eurosceptic press, half of respondents to the Mori poll are still in favour of British membership of the EU, compared with 41 per cent against. It will therefore be helpful to remind voters of the advantages a Yes vote would bring to Britain’s position in Europe, as well as the disadvantages of a No vote, including the possible threat to membership. However, it would be unwise to overstate the membership issue or to rely solely on strategic arguments. Details of the treaty also need to be disseminated and explained.

At present a major disadvantage for the Yes campaign is the widespread ignorance about the European constitutional treaty in particular and the EU in general. This allows the Eurosceptic press to print scare stories and misinformation – such as claims that the constitution will be a threat to national identity or lead to a European super state. The public is entitled to demand that the government publishes a summary of the treaty, which should be available in every post office. This should work to the benefit of the Yes camp; Mori shows that the more people know about the EU, the more likely they are to support the constitution.

The passage of the necessary legislation for a referendum during the autumn and winter ought to be a signal for a concerted effort to explain the advantages of the constitutional treaty. A failure to act by pro-Europeans risks allowing opinion against the constitution to become set in stone, making a Yes victory more difficult.

Lord Radice is a board member of Britain in Europe.

Published in The Financial Times on 6 September 2004, http://www.ft.com