To Barack Obama and Sarah Palin, she's the eccentric author of those letters about polar bears and seals. To the French legal system, she's a five-times offender of incitement to hatred. To millions elsewhere, including those who've never seen one of her 48 films, she is forever BB, Brigitte Bardot, the immortal sex kitten who refuses to purr obediently into old age. During the 1950s, she popularised topless sunbathing and put St Tropez on the map long before it became known as fake tan. A true original, every decade since has thrown up pretenders to the Bardot throne, with her tousled blonde beehive and pout endlessly re-invented by actresses, singers and fashion models. Like her American counterpart Marilyn Monroe, Bardot's acting skills were best suited to light-hearted comedies. And while, like another screen icon, Greta Garbo, she came to film in her teens and retired early, Bardot was never destined to play the theatrical tragic heroine or a Queen Christina. But her extraordinary appeal went somewhat beyond that of vacuous sex symbol, a factor remarked upon by none other than existentialist writer Simone de Beauvoir who, ironically, saw Bardot as a totally liberated woman, a kind of pre-feminist feminist.

"It was extraordinary to see, especially at a time when no women were allowed to be (liberated). She lived the way she pleased, she dressed the way she wanted; in that sense her freedom was very provocative." Sensuality was suggested rather than obviously flaunted, and unlike her sophisticated '50s contemporaries Sophia Loren and Gina Lollobrigida, the girlish Bardot eschewed their plunging necklines and stilettoes in favour of her signature off-the shoulder dresses and tight T-shirts, Capri pants and ballet pumps. The contrast with Loren continues to this day: the 75-year-old Italian actress has resorted to plastic surgery to slow the effects of ageing; Bardot, resolute as ever, will have nothing to do with the surgeon's scalpel.

The naturalness and poise celebrated by de Beauvoir and others was evident from an early age. Born into a middle-class Catholic family in Paris, she was nicknamed Bri-Bri after a doll her mother, Anne Marie, once owned as a child. Although a teacher at the private school attended by the then nut brown-haired little girl with the wire-rimmed glasses described her as "terrible" and "she won't go anywhere", Brigitte showed a natural talent for dancing. Her mother encouraged both her and younger sister Mijanou to attend ballet classes and this led to enrolment at the Paris conservatory when she was 13, alongside classmate Leslie Caron, future star of Gigi.

But a career as a dancer took a back step when she appeared on the cover of Elle magazine. The shot famously came to the attention of director Roger Vadim who wrote to her parents requesting permission to screen test the 15 year-old for a film project. "Two things struck me about her: first, her style; the way she would walk, move, look at people. She was also, for a little bourgeois, very revolutionary," he said.

But the budding star quickly became disillusioned with her acting ability and declared her very first film, Le Trou Normand, as terrible. The second, she believed, wasn't much better. But Vadim convinced her to persevere and encouraged her to attend drama school. "Vadim was the only man who was certain I had something special to offer on screen. I placed myself entirely in his hands." They married when she was just 18.

It wasn't until four years later that Bardot starred in the film that eventually transformed her into an international sex symbol. Et Dieu... Créa La Femme (And God Created Woman) scandalised America with its central character Juliette, an amoral young woman given to much flirting when not dancing barefoot in sweaty nightclubs. But for all her beauty and poise, Bardot confessed to Vadim that she felt ugly and hideous. Biographers refer to her suicide attempts at 15 and then 26.

Relationships were doomed never to last; her marriage to Vadim floundered during the filming of And God Created Woman; she began a two year affair with co-star Jean-Louis Trintignant; he moved in with actress Annette Stroyberg who gave birth to their daughter shortly after he and Bardot divorced. Bardot sought brief comfort in singer Sasha Distel, then married actor Jacques Charrier in 1959 and gave birth to her only child, Nicolas, the following year. After her 1962 divorce from Charrier, she gave over custody and the entire care of her baby son to her ex-husband. She didn't like being pregnant, and dreaded childbirth, as she recalled in a frank interview in the 1970s. "I think I'm not made to be a mother. I don't know why this is because I adore animals and I adore children, too, but I'm not adult enough to take care of a child."

Shortly after retiring from films in 1973, Bardot set up her Foundation for the Protection of Distressed Animals. Recent activism includes writing to President Obama, expressing her "immense hope" that he will speak out against Canadian seal hunting. She was less complimentary last year to Sarah Palin, criticising the Alaskan governor's support for wolf hunting and oil drilling in an Arctic Wildlife refuge. "I beg you no longer refer to yourself as a pit bull with lipstick, as no pit bull, no dog, is as dangerous as you."

Her racist remarks directed at France's estimated 5million Muslims, coupled with some homophobic comments, fly in the face of the French avowal of liberty and equality. But at 75, the world's revolutionary 'sex kitten' really doesn't care. The only thing that remains silent about her is the 't' in that famous surname...