PRESIDENT CHIRAC this week will attempt to persuade disgruntled voters to put aside their grievances and approve the European Union constitution, after a poll yesterday showed the “no” camp surging ahead eight weeks before the French referendum.

The French head of state, who has held fire in the debate so far for tactical reasons, is to enter the campaign fray in a television debate with young people on Thursday evening. With his presidential legacy in jeopardy, he knows that he must deploy his formidable powers of persuasion to turn the tide and save a campaign that is taking on the flavour of a potential rout.

M Chirac will try to convey a solemn message: that history and the nation’s destiny call for a “yes” to a project that caps five decades of French leadership in Europe.

Rejecting the constitution would humiliate France and wound the EU, making it less able to stand up to the forces of “American-led globalisation”, he will say.

Dominique Perben, the Justice Minister, put the Government’s killer-argument more bluntly last week: “We have finally obtained this ‘Europe à la Française’ that we have awaited for so long,” he said. “This constitutional treaty is an enlarged France.”

Six opinion polls over the past month have shown the “no” supporters leading. The latest yesterday, by Ifop for le Journal du Dimanche, found that the “no” camp had risen to 55 per cent among certain voters, compared with 61 per cent for a “yes” in February. The undecided vote has shrunk from 45 to 37 per cent.

The highest “no” figures yet show that a week of energetic campaigning by the Government of Jean-Pierre Raffarin and the leadership of the pro-constitution Socialist Party had failed to dent the determination of voters to use the May 29 referendum to blow a Gallic raspberry at M Chirac, the political establishment and the EU.

Ministers are talking privately of their belief that the referendum is falling victim to anger over rising unemployment, economic stagnation and a broad sense of injustice over government policies. The vote could turn into one of those springtime revolts that punctuate French history.

Many centre-right voters who normally back M Chirac believe that voting “no” is a cost-free way of signalling their displeasure. A majority of the Socialists’ usual electorate has swung behind voting “no”, believing that François Hollande, the party’s leader, should not be consorting with the “enemy” — the Chirac camp.

Support for rejection is spreading into unlikely sectors, such as the business world and the professional classes. Farmers, who benefit hugely from the EU Common Agricultural Policy, which absorbs almost half the EU budget, have turned nearly unanimously against the constitution.

The poll yesterday found that support for the treaty was solid only among voters of the small centre-right Union for French Democracy party, a government ally that was founded in the early 1970s by Valéry Giscard d’Estaing, the former President who chaired the drafting of the constitution.

M Chirac’s team and M Hollande, leader of the Opposition, had been hoping to cool the mood of revolt by extolling the merits of a constitution that was proposed by M Chirac and drafted under French leadership. The latest poll showed that a majority of voters claim to be basing their decision on the contents of the constitution, with France’s economic situation as the close second factor.

The “yes” campaigners believe that voters have not focused on the reality of the complicated 240-page treaty. This is because the rejection front — an unholy alliance of rightwingers, National Front supporters, Trotskyites and traditional Socialists — are successfully avoiding the true contents while exploiting general unhappiness over the enlargement of the EU into what France sees as a British-dominated free market.

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