“BANG, bang,” she sings, seductively pointing a make-believe gun at a long black limousine, which bursts into flames. Expected on television in France at the end of this month, the advertisement for the new Lancia Musa car is also an eye-catching introduction to France’s first lady in waiting.

A highly paid model and folk singer, Carla Bruni, the temptress in the Lancia advertisement, makes an unlikely presidential muse. But instead of embracing the novelty of a glamorous working girl as “première dame”, France seems divided over Nicolas Sarkozy’s decision to marry her just three months after reluctantly getting divorced from Cécilia, his second wife, who left him for another man.

The elegant, long-legged Bruni, 40, is certainly not Bernadette, matronly spouse to Jacques Chirac, the former president, whose interest in roses and promoting children's charities endeared her to an older, conservative generation.

It is among these traditionalists - as well as among the poor - that support for Sarkozy has eroded most noticeably of late, prompting jitters among presidential aides who had expected the nation to rally to the spectacle of love blossoming in the Elysée.

A wedding was thought to be imminent. Although this would resolve awkwardness during overseas visits, it has prompted objections that the “hyper-president” is moving too fast after falling in love with Bruni at a dinner party only two months ago.

“People are worried for the happiness of the president,” said Nadine Morano, an MP and Sarkozy supporter.

Others complained, less charitably, of the way in which “speedy Sarko” had paraded Bruni in public on visits to Egypt and Jordan. This week, when she joins him at the end of an official visit to India, they will marvel at the Taj Mahal. But Sarkozy was said to have cut short the private part of the programme to avoid more talk of him flaunting his good fortune.

The damage, however, is already done and there are fears that the governing Gaullist party could lose ground in municipal elections in March.

“When I voted for him last year I didn’t know Nicolas Sarkozy was such a show-off,” said Marie-Elène Mulot, a retired teacher and former Chirac supporter as she shopped for groceries in Paris on Friday. “And I certainly didn’t think that we ran the risk of having Carla Bruni as first lady. All this vulgarity makes me ashamed for France.”

She is not alone. When the internet edition of the conservative Le Figaro newspaper invited readers to debate whether Bruni “would make a good first lady” it was swamped with largely negative responses about her reputation as a serial “man-eater” who is on record as saying, “Monogamy bores me terribly.”

“She is unstable, hardly much of an example for our youth,” wrote one of the participants.

Bruni’s long list of conquests includes Sir Mick Jagger and Eric Clapton, the rock stars, and Donald Trump, the American billionaire. She is famous for leaving Jean-Paul Enthoven, a publisher, for his son, Raphaël Enthoven, a philosopher. A novel written by the junior Enthoven’s heartbroken wife about the affair depicted Bruni as a woman “beautiful and bionic, with the look of a killer” and known as “the Terminator”.

Bruni had a son with him, Aurélien, and images of the six-year-old astride Sarkozy’s shoulders in the ancient pink city of Petra in Jordan over the holidays prompted a complaint from the father that the boy was being used as a political prop. Others accused the president of insensitivity to Louis, his 10-year-old son by Cécilia.

At the same time there were worries that Bruni, who voted for Ségolène Royal, the Socialist candidate, in last year’s election, might lead Sarkozy astray from his goal of modernising France through social and economic reforms. A spoof Bruni diary in one newspaper had the singer threatening Sarkozy with a “sex strike” if he tried to do away with the 35-hour working week.

Another example of the ribaldry provoked by the relationship was one columnist’s advice to “keep her away from your sons” - a reference to Sarkozy’s two good-looking elder sons from his first marriage.

“At this rate we might even end up missing Bernie,” one critic wrote on Le Figaro’s forum, referring to Bernadette Chirac. “At least there is little danger of it lasting for a whole five-year presidential term. Bruni seems to like a new man every week.”

Few seemed to consider Bruni might be better equipped than most for a gig at the Elysée, and not just because of all the bed-hopping that has gone on there of late. She grew up in an Italian palace, the stepdaughter of Alberto Bruni Tedeschi, an Italian tyre magnate and classical composer, and Marysa Borini, a concert pianist. She was educated in France, where her family moved in the 1970s to escape a wave of kidnappings in Italy. She is rich, intelligent and speaks three languages.

“She knows how to behave at state banquets, she knows about current events, poetry and art,” said one fashion journalist. “Why should anyone care if she has been photographed in the nude?”

She can hardly do worse than Cécilia, who famously failed to turn up for a picnic with the first American family and says she prefers a life in the shadows.

Bruni’s star power, by contrast, sets things alight. The trick for Sarkozy will be to stay out of the flames.

Watch Bruni's advertisement

Times Recommends

• 'Radio Rancid' is scourge of Obama
• French gulp as global warming alters wines
• Colton, the barefoot boy bandit, outfoxes sheriffs