Franck Ribéry is the focus of his country's World Cup hopes. But that doesn't make him universally popular as John Lichfield reports from Boulogne

Any Channel sea-farer landing in Boulogne-sur-Mer this month – in fact anyone travelling anywhere near to the town – will be confronted with a giant poster of a frowning, unshaven, young man.

He stares across the harbour to the offices of the "humane shipwreck society" and the Nausicaa aquarium and oceanic study centre with an unsmiling expression of puzzlement or suspicion. It is not a pretty picture but it could have been much worse. Madeleine, 56, came to the Boulogne quayside with her husband and son to photograph the giant photograph. "Luckily, they've shown the right hand profile of his face," she said. "You don't see his scars that way."

The young man in the giant portrait, 90ft high and 100ft wide, visible from the Paris autoroute two miles to the east, is Franck Bilal Yusuf Mohammed Ribéry, born in April 1983 in a troubled estate in Boulogne-sur-Mer. Franck is a local hero and should be a national hero.

France's hopes of winning the football World Cup in South Africa this month and next rest mostly at Franck's feet. He is the most talented player, as winger, or striker, or play-maker, in the French squad – the Gallic Wayne Rooney. The decision by Nike, the sportswear company, to erect a giant portrait of Franck in Boulogne follows the company's erection of a slightly smaller poster of Zinedine Zidane, local hero and global superstar, at Marseilles before the 2002 World Cup.

The Zidane picture became an icon. The giant portrait of Franck's head – like the unfortunate incident with Thierry Henry's hand in the qualifying play-off game with Ireland in November – has come to symbolise the ambivalent feelings of many French people towards "Les Bleus", their national football team.

Zinedine Zidane, now retired, is a handsome man who looks rather like Mr Spock from Star Trek. Franck Ribéry, whose face was shattered in a car crash when he was two years old, is not an obvious candidate for a giant blow-up photograph. When he played for Galatasaray in Turkey, the local fans, who loved him dearly, called him "Scarface" and "Franck N Stein". However, that does not explain why the giant portrait in Boulogne-sur-Mer is controversial. Franck Ribéry, supposedly a home-loving, family man and devout converted muslim, is one of three France footballers under investigation for visiting an "under age", high-price prostitute in a bar just off the Champs-Elysées in Paris.

Zahia, who has sold her story to a French magazine in a very British way, was not under the age of sexual consent. She was 17 when she was offered to Ribéry by some of his team-mates as a "birthday present".

Under French law it is illegal to pay for sex with a girl under the age of 18. Zahia has told investigators that she lied to Ribéry, and the others, about her age. The footballers are therefore unlikely to be prosecuted.

All the same, the revelations have soured an already difficult relationship between the French public and its under-performing national football team. Last month the regional council for Nord-Pas de Calais, withdrew its permission for the giant Ribéry portrait to be built over the remains of a wartime German bunker in Boulogne harbour. Daniel Percheron, the Socialist president of the regional council, sent a pompous letter to the advertising agency involved in the project. "The media hubbub attacking, rightly or wrongly, Franck Ribéry, leads us to believe that a poster of Monsieur Ribéry could be regarded as a provocation against the deepest feelings of public opinion," he wrote.

Most politicians in Boulogne supported the giant portrait. Regional politicians were divided. The local baroness of the far-right National Front, Marine Le Pen, daughter of the party's founder, said that Ribéry was a "perfect international... some-one who sold out to global commercialism" (he plays for Bayern Munich)" and is now "accused of grave incidents with a minor".

The Socialist mayor of Boulogne-sur-Mer, Frédéric Cuvillier, said the attempt to ban the giant poster was "ridiculous and shocking". Nothing had been proved against Ribéry. The accusations were just "rumours and random news items".

Last week, Mr Cuvillier triumphed. The regional council relented and nine rock-climbers were hired to erect the giant photograph overnight. "No one ever mentioned Boulogne-sur-Mer before, even on the TV weather forecast," the jubilant mayor said. "Now everyone knows where we are."

Judging by conversations with people on the harbour and streets of Boulogne, the mayor made the right decision. "Franck is very popular here," said Madeleine, as her son took photographs of the giant photograph. "He comes back often to see his parents. He hasn't forgotten where he came from. I feel sorry for his wife but all of this business should be between him and her."

Wahiba Ribéry – of Algerian origin but born in Boulogne – was Franck's childhood sweetheart. He converted to Islam, and took on several new Islamic first names, after they married in 2004. They have two children.

The fact that one of the few white players in the France squad converted to Islam helps to explain the xenophobic National Front's hostility to him. Ribéry raises his hands to Allah before each match but is reluctant to talk about his religion.

"As a kid, I spent all my time with Muslims," he once said. "It is my choice. No one told me to (convert). I prefer to keep my reasons to myself."

Ribéry, known for his dribbling, has followed a zig-zag route to football success. He is not so much a product as a reject of the prolific youth academy system of the large French clubs. He was expelled from the Lille academy at the age of 16 in 1999 because he refused to do his school work and fought with the other kids. Ribéry played in junior leagues in Turkey before his talent was recognised in France. The fact that he was booted out by Lille for flunking his academic work has created an impression that Ribéry is dim-witted.

Not true, said Jean-Luc Vandamme, the man who brought him to Lille's youth academy at 13 (and later fired him). "People think that he's thick but that's pure stupidity," Mr Vandamme said. "He is anything but. He has a practical intelligence, like all the great players." One of his early coaches in Boulogne, Jose Pereira, said: "Even a street lamp would have seen that Franck was a very good player but you had to watch him like a pan of milk on the boil. He was a kid who had grown up in the street."

Ribéry lived as a child in the troubled Chemin-Vert estate on the hill above Boulogne. His maternal language is not classical French but the northern patois called "ch'ti", a mixture of French, Picard and Flemish.

Ribéry often returns to Chemin-Vert and, according to locals, is never empty-handed. He always bring football shirts, boots and match tickets for local kids and youths. He earns €8m a year and is said to be generous.

On the seafront in Boulogne, two 15-year-old boys, Joey and Joevil, were smoking cigarettes when they should have been in school.

What did they think of the giant tribute to Ribéry just across the water? "We like it," Joey said. "Ribéry is a big hero here. He was a kid who came from a bad estate and people wrote him off. But in the end he made it big. Best of all, he escaped from Boulogne."