IT READS like the synopsis of a trashy airport novel: sex, movie stars, politicians, Arab princes, arms deals and the courageous investigation of an obstinate, incorruptible - and publicity-hungry - judge. But the evidence to be presented to a criminal court in Paris this week also has a disturbing side - or, rather, two disturbing sides.

The case uncovers the brutal methods used to snare young women - some as young as 15 - into a call-girl agency specialising in wealthy, high- profile clients. It also exposes attempts by the French government machine to block an investigation which might embarrass senior politicians and damage French interests abroad.

Six people are charged with the running of an international prostitution ring, whose call-girls entertained the actor Robert de Niro, the former tennis player, Wojtek Fibak, two senior (but unnamed) French politicians and several Gulf princes. The agency specialised in tricking, or trapping, star-struck teenage girls into selling their bodies with the promise of careers as models or actresses.

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At one point, according to the report of the investigating judge, the agency became a kind of approved dealer in girls, operating with the connivance, if not the blessing, of the French foreign ministry and French secret services. By steering Middle East arms clients towards girls from a known, and closely watched, agency, there was thought to be a reduced risk of blackmail, or the leaking of secret negotiations.

Leaks from the French investigation last year suggested that the agency once brokered a $1m (pounds 625,000) deal for an Arab prince to spend a night with a Hollywood actress. The woman named by French magazines at the time has adamantly denied the story. The allegation does not form part of the final judicial report.

The two principal accused are Jean-Pierre Bourgeois, 51, a failed fashion and glamour photographer and Annika Brumark, 50, a Swedish former model and one-time beauty queen. They, and four others, will be charged before the Tribunal Correctionel in Paris tomorrow with procurement or complicity in procurement. (Prostitution is legal in France; procurement is not.) Mr Bourgeois also faces possible additional charges of rape.

The French Brigade de Repression de Proxenetisme (the equivalent of the Vice Squad) traced 89 young women - would-be models or actresses - who said they had been tricked or sometimes physically constrained by Ms Brumark and Mr Bourgeois into working for them. According to the judicial report, the girls were sometimes "sold on like cattle" to other call- girl agencies.

The files of clients' names seized by the police are said to include many well-known members of the sports and show-business jet-set on both sides of the Atlantic. The only names to emerge so far are De Niro, Fibak and the French film producer, Alain Sarde.

De Niro, despite a much publicised "arrest" in Paris while filming a movie earlier this year, was questioned only as a witness and occasional client of the network's prostitutes. He is suing the investigating magistrate, Frederic N'Guyen Duc Quang, following his highly publicised interrogation; the actor's lawyers accuse the investigator of deliberate publicity-seeking. Messrs Fibak and Sarde are the subject of a separate judicial investigation.

The client list is also said to have included two senior French centre- right politicians, whose names have not been leaked. Both the French foreign and interior ministries tried to squash or limit the investigation in its early months - the interior ministry because of the possible embarrassment to senior politicians, the foreign ministry because it did not want to upset Middle Eastern buyers of French armaments.

Judge N'Guyen is one of a new breed of judicial investigators in France who refuse to bow (as their predecessors routinely did) to political pressure. Even so, he only began to make real progress when the centre- right French government fell in June last year and was replaced by a Socialist- led government.

According to Judge N'Guyen's report, the photographer, Mr Bourgeois, hung about Parisian night clubs or casting agencies, scouting for possible victims. He picked on young women, often teenagers - mostly French, but also from Britain and eastern Europe - and invited them to his apartment in the respectable 17th arrondissement to take trial shots.

After gaining their confidence, the judge alleges, he persuaded them to pose for more revealing pictures. The girls were then convinced, if possible, that prostitution was the best way to get into modelling or movie careers. If they refused, they were blackmailed with the threat that the photographs would be sent to their families. In some cases, they were simply abducted. Several girls cited in the investigating judge's report accuse Mr Bourgeois of rape.

Pictures of the girls were then circulated among possible clients. The presence on the client list of a well-known movie producer such as Mr Sarde allegedly helped Mr Bourgeois and Ms Brumark to perpetuate the myth that prostitution was a prelude to stardom.

The agency's downfall came soon after it expanded to the lucrative Gulf market in 1996, with the alleged help of a third accused, Nazihbdullatif al-Ladki, a Lebanese businessman. Mr Bourgeois, according to the indictment, travelled to Latvia to scout for more victims, but his activities were reported by a local model agency and the French vice squad was alerted.