France’s obsession with its late bad-boy of song, Serge Gainsbourg, has reached new heights with the release of a flattering new biopic that does little to challenge his image as the ultimate poetic anti-hero.

Nearly 20 years after Gainsbourg drank himself to death in Paris, the country remains mesmerised by the memory of a man seen widely as both an inspirational wordsmith and the epitome of romantic Gallic cool.

Today his grave in Montparnasse cemetery is still the most visited in the country – regularly adorned with offerings of cigarettes, candles and metro tickets – while the walls of his house on the Left Bank are scrawled with adoring graffiti. Universities teach his lyrics.

Gainsbourg’s wife and long-time muse, the English actress Jane Birkin, continues to perform his songs and has almost as mythic a status among the French public as he does, while their 38-year-old daughter Charlotte Gainsbourg is an award-winning actress and singer.

In the musical world, he remains a reference to France’s emerging artists, while abroad he is one of the few to escape the widespread contempt for rock à la francaise, being cited as an influence by groups including Sonic Youth and Portishead.

But such is the sacrosanct aura surrounding Gainsbourg that the darker sides of his complex character have been air-brushed out of the picture … most notably his obsession with the sexual attractions of under-age girls.

Until now, as the challenge is finally taken up by Johann Sfar, no film-maker has dared portray so beloved a national icon. And Sfar’s career has been not in cinema but in Bandes Dessinées or graphic novels. He is the author of the internationally acclaimed The Rabbi’s Cat series of comic books.

Sfar’s Serge Gainsbourg: A Heroic Life opened on Wednesday to rave reviews, with much comment focusing on the extraordinary likeness of the lead actor Eric Elmosnino. The film also stars Laetitia Casta as a gorgeous Brigitte Bardot, and in the central role of Birkin the late British actress Lucy Gordon.

Gordon committed suicide last May shortly after filming finished, and Sfar has dedicated the movie to her memory. “She seemed to be the happiest of people and she loved the work. She came to the set even when she wasn’t needed. We were all devastated that she decided to end her life,” Sfar told the Sunday Herald.

Sfar says he wanted to avoid the biopic conventions, instead seeking out “deeper poetic truths”. The clearest sign of this is the inclusion of a kind of evil alter ego … a caricature of Gainsbourg with exaggerated nose and ears who accompanies him throughout.

However, otherwise the film follows a rigidly linear path through Gainsbourg’s 62 years. Born Lucien Ginsburg in 1929, he wore a yellow star under Nazi occupation and discovered his talent for music in the jazz-clubs of post-war Paris.

He began by writing songs for other artists – including bizarrely a Eurovision entry for France Gall in 1965. His performing career only took off after his meeting with Birkin in 1968. Their co-production Je t’aime, moi non plus was banned by the BBC for its explicit sexuality, though the controversy meant the song’s highly subtle lyrics went unappreciated.

But in 1981 Gainsbourg’s drunkenness caused the break-up of his marriage to Birkin. In the last 10 years of his life he developed a provocative new persona – dubbed Gainsbarre – and entertained the French with ever more outrageous behaviour, setting fire to a 500 franc note on live television for example, and propositioning Whitney Houston.

Today it is impossible to exaggerate the degree of reverence still felt among the French towards a figure who clearly encapsulated a kind of idealised national self-image. His combination of poetic sensibility, fatalism and man-of-the-people irreverence answers something deep in the modern French psyche.

“He’s even more appreciated today than he was the day he died … and, my God, the day he died the nation was in mourning,” Birkin said in an interview.

“He had so many sides. There was an instinctive generosity that came from his Russian background. There is the whole travelling Jew thing. His humour is out of Woody Allen or Mel Brooks. And then there is the poetry. He adored words and played with them in a

way that the French never had before,” she said.

According to Olivier Nuc, music critic of Le Figaro: “I grew up in the 70s and back then he and Birkin were everywhere. He loved people and people loved him. He had absolutely no

snobbery. Even though he was rich and intellectual, he always kept that popular attraction. Really he’s never left our lives.”

“Gainsbourg was a highly provocative character, but people loved him,” agreed Sfar. “Perhaps it was because they could see he was fragile, that he wanted to be loved. He was always eager to do beautiful things, even if they were also shocking.”