Buoyed by polls showing increased support for the constitution, M Chirac endeavoured, in a live television interview, to present it as a triumph for Gallic diplomacy. “My belief is that this constitution is essentially of French inspiration,” he said, arguing that its origins could be traced back to the fall of the Bastille. “It is the daughter of 1789 through its ambition and through its respect for human rights and democracy.”

With the “yes” camp holding a slender lead in the polls for the first time since March, the head of state set out to counter opponents who say that the constitution would dismantle France’s centralised State and undermine its public services.

Claiming that France was the only EU country not to have made a single significant concession during the negotiations, he said: “The constitution is the best possible one for us.”

The 72-year-old President was making his second television appearance of the knife-edge campaign. He has tried to reassure Eurosceptics concerned that the constitution would undermine French sovereignty. The treaty laid to rest the idea of the United States of Europe, he said, claiming that it promoted instead an “organisation that enables us to work together when that is most efficient but where each state, each nation preserves its identity, and therefore its culture and its interests”.

But the President’s main target was the Socialist voters who threaten to tip the balance towards the “no” camp. He repeatedly insisted that the constitution would protect the “French social model” and act as a barrier against Anglo-Saxon liberalism. “This is a decisive step towards a better social situation,” he said. “We fought for recognition of public services — and at one time we were alone — and we have won.”

M Chirac said a victory for the “no” camp would “interrupt 50 years of European construction, and mean returning to existing treaties, which everyone says are insufficient”.

Turning his opponents’ arguments on their head, he added that a French rejection of the constitution would “leave the road clear for those who want Europe to be a free-trade zone and not a social organisation”.

In a clear message to wavering Socialists, he said: “I respect people who are against Europe for personal beliefs, but you can’t vote ‘no’ and say you are in favour of Europe.”A “no” vote would be a failure for France, would leave the country isolated and weaken its voice, not only in Europe but internationally, he said.

M Chirac also wanted to dismiss suggestions that the EU had a fallback if the “no” camp prevailed. “There is naturally no Plan B,” he said, implying that the result would be chaos.

The French President is hoping to surf on a wave of support that has come after public calls in favour of the constitution from Gerhard Schröder, the German Chancellor, Jacques Delors, the former European Union President, Valéry Giscard d’Estaing, the former French President, and Lionel Jospin, the former French Prime Minister. At a ceremony at the Elysée Palace for European celebrities on Monday, the President also won precious backing from Johnny Hallyday, the iconic French rock star, who said: “We French cannot stay outside Europe.”

The successful launch last week of the A380 Airbus super-jumbo was also portrayed as evidence that Europe can offer France la grandeur it used to enjoy on its own.

Another factor in the turnaround in the polls may be the €400 million (£270 million) spent by the French Government to appease a variety of lobbies: civil servants have been given a 1.8 per cent pay rise, farmers have been offered paid holidays, wine producers more subsidies and hospital doctors a budget increase.

With discontent still rife and M Chirac’s centre-right Government deeply unpopular, the referendum’s outcome is uncertain. M Chirac says that he will not resign if there is a “no” vote and has hinted that he will dismiss his lame-duck Prime Minister, Jean-Pierre Raffarin, even if it is approved.

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