By Caroline Wyatt
BBC News, Paris
The French government is stepping up its campaign in support of the proposed EU constitution after five consecutive opinion polls suggested voters might reject it in a referendum in May.
Nicolas Sarkozy has been pushing the Yes campaign
An opinion poll in the newspaper Le Figaro suggests 54% of the French would vote No, while a separate poll for Paris Match magazine on Tuesday gave the No side 53% of the vote.
A similar poll a few months ago had estimated the No vote at only 40%, and until now, France's ruling elite has taken French support for Europe for granted.
For the past months, the Yes campaign has been all but invisible, while a disparate group of Eurosceptics, the far left and some Socialists has been campaigning vigorously across the country for a resounding No.
Those who would reject the EU constitution have found a receptive audience in France, where voters are increasingly fed up with Jacques Chirac and in no mood to listen to the government.
Instead, a significant majority of the French seem to be planning to use the 29 May referendum to send a clear message of discontent to their president and his ruling centre-right party.
Their dissatisfaction stems as much from domestic issues such as high and rising unemployment, as over growing French unease about the direction Europe is taking.
EU enlargement to 25 countries - including many in eastern Europe - has made some in France feel Paris has less influence in Brussels, and is no longer leading Europe at all, despite France being a founding member.
French Prime Minister Jean-Pierre Raffarin has been reduced to pleading with the voters, saying that a Yes vote for the constitution will not be interpreted as approval for the government.
At the same time, President Jacques Chirac made a point of standing up to Brussels at the last EU summit to demand it withdraw measures to liberalise services in an attempt to prove that he is a vigorous defender of French interests.
But his tough stance appears to have made little difference to French voters - if anything, support for the No vote has risen since that summit.
The most unexpected twist to the EU referendum in France is the strength of feeling among the opposition Socialist party.
Its leader Francois Hollande won an internal party vote in December to campaign for a Yes vote, even though that meant siding with the government.
That is a decision Mr Hollande may come to regret as he faces mounting opposition from within, with the latest poll for Le Figaro newspaper suggesting that 53% of French Socialists plan to vote No.
Their reasoning is that the constitution as it stands is too liberal, too "Anglo-Saxon" and would not protect the French social model.
Socialist critics, and many on the right as well, fear the French work force would suffer from outside competition, not least from cheaper Polish plumbers or Lithuanian lumberjacks if services are liberalised.
And the debate is getting increasingly personal. One French Socialist MP is threatening legal action against the British Minister for Europe, Denis MacShane, for calling French opponents of the EU constitution "neo-cretins".
"I was shocked and deeply offended by his comments," says Arnaud Montebourg, a radical French Socialist who is campaigning for a No vote.
Wider voter concerns could boost the No campaign
Mr MacShane said he had not meant to cause any offence in his speech in French to students in Bordeaux last week, in which he emphasised that a French "Non" would be a "disaster for Europe".
Mr Montebourg took umbrage at Mr MacShane's French pun when he urged students not to listen to "reactionaries, neo-conservatives, neo-communists and 'les néo-cons' who are trying to persuade you that voting No to the treaty is a good thing".
A "con" is a widely-used French insult which can be translated as "a bloody idiot, damned fool or cretin". Mr Montebourg, a lawyer, told the BBC that if he did not receive an immediate apology in writing, he would pursue his action for slander.
It seems that the EU referendum has become a lightning rod for France's various discontents, and could prove deeply divisive here.
A French Non would create shock waves in Brussels, as a rejection by one of the key founding EU members would send the constitutional treaty straight back to the drawing board.
No bad thing, say its critics here.