Two of France's biggest international football stars are to face trial for allegedly soliciting an underaged prostitute, in one of the most high-profile sex scandals to hit French sport.

Franck Ribéry, who plays for the German club Bayern Munich, and Karim Benzema, a striker at Real Madrid in Spain, have been ordered to stand trial over allegations of paid sexual encounters with Zahia Dehar, who was under 18 at the time. They will appear with six other defendants, some of whom will be prosecuted for "aggravated pimping".

The long-running case, which began as a police investigation into allegations of prostitution at an expensive nightclub near the Champs Elysées, tarnished the image of French football, upset the French team during its fraught 2010 World Cup campaign in South Africa and has since become an extraordinary celebrity saga in France.

Dehar told investigators that Benzema had paid for sex with her in 2008, when she was 16. She further claimed that Ribéry had paid sex with her the following year. He allegedly flew her to Munich as a 26th "birthday present" to himself. Ribéry, a convert to Islam who is married with three children and had been hugely popular in France for his image as a wholesome family man, told police he had not known Dehar was underage.

Asked by Paris Match magazine whether she had been Ribéry's birthday gift, Dehar replied: "I'm a pretty present, aren't I?" She told investigators that neither footballer had known her real age.

In November last year, the Paris state prosecutor requested that the case against the footballers be dropped on the grounds that they did not know that Dehar was under 18. But the investigating judge in charge of the case decided differently and this week sent it to trial. Both players face a possible three years in prison or a €45,000 (£35,000) fine if found guilty.

When the footballers were first placed under formal investigation in July 2010, Ribery's lawyer said a legal case would have to prove that the player had known Dehar's age "which isn't the case". Benzema's lawyer said on Tuesday he was "innocent" and would explain himself in court.

The case, which began in 2009 when police were investigating an alleged pimping network in a central Paris bar called the Zaman Cafe, has in recent months moved from the crime and sports pages to the fashion sections. Following the exposure of the high-profile investigation, the fashion designer Karl Lagerfield has taken the Algerian-born Dehar, who is now 20 and a designer, under his wing and her own lingerie collections have shown at Paris fashion week. Artists Pierre et Gilles have painted her and she has graced the covers of glossy magazines.

But the three-year legal investigation into alleged pimping and illegal underage sex pointed to a harsher reality behind the glamour of Paris's top bars, where Dehar said she once met clients. Born in Algeria, Dehar moved to the Paris suburbs after her parents' divorce and began going to VIP bars in central Paris in her teens.

Didier Deschamps, the new French football coach, said he did not want to comment on the case. "It's in the hands of the justice system," he said. "It won't change my demands as to their behaviour on and off the pitch as part of the French team."