Beyond the criminal allegations being aimed at former president Nicolas Sarkozy, the most explosive legal case in France at the moment is centered on his protegee, Rachida Dati.

Lawyers for the former conservative justice minister will be at the Tribunal de Grande Instance in Versailles next week, where judges will hand down a ruling with potentially massive financial consequences. Dati has named the casino and restaurant tycoon Dominique Desseigne as the father of her only child, now three. Desseigne, who is one of France's richest men, is reportedly refusing to take a DNA test, but the court ruling could order him to co-operate. A positive result would entitle both mother and child to a multimillion-euro stake in his fortune.

If it already sounds like a Gallic Dallas, it gets worse. Desseigne has offered the names of seven other "famous men" who were said to have had overlapping affairs with Dati in the year during which the child was conceived – from other big-shot businessmen, through a TV star and Qatari prosecutor, to a younger brother of Sarkozy. If nothing else, Dati's case illustrates the appalling image female politicians have in France at the moment. While men's alleged illicit affairs are still viewed as inconsequential, they always come to define their female counterparts.

Dati was made France's first female justice minister from an ethnic minority just five years ago. The so-called garde des sceaux, or "keeper of the seals", is a position stretching back to before the 1789 revolution, and has been occupied by some of the most distinguished politicians in history. Yet Dati's watch was summed up by Judge Bruno Thouzellier as showing "frivolity in the face of hardship". Rather than implementing much-needed reforms of France's legal system, Dati is accused of concentrating on media appearances and her celebrity love-life.

In some ways the surprise is that we know as much as we do. The Dati v Desseigne judgment comes at a time when the alleged sexual incontinence of French public figures is making headlines like never before. From the orgies and alleged sexual brutality of former Socialist presidential hopeful Dominique Strauss-Kahn to the fraught domestic life of President François Hollande, secrets once guarded by strict privacy laws and a reverential press are bursting into the open. Media observers believe that the Strauss-Kahn scandal served to embarrass the French press, who are now attempting to make amends of sorts. Only last month it was claimed that the Socialist head of state was at one stage been "sharing" his then-mistress, Valérie Trierweiler, with the conservative minister Patrick Devedjian.

The well-documented affairs of head of state, Jacques Chirac, are part of an adulterous tradition involving pretty much every president, including the Socialist François Mitterrand who kept "a secret family" at the taxpayers' expense. Dati, who as a minister made much of her preferences for stilettos and designer work clothes in interviews and photo shoots with Paris Match, fitted straight into the macho, sexist culture of French politics in a manner matched by first ladies Trierweiler and her predecessor, Carla Bruni.

These are the women currently associated with French politics. Very few people outside of the country would be able to name a single female minister at the moment.

Yes, Hollande has ensured a cabinet of gender parity, but the big jobs – prime minister, foreign minister and interior minister – all went to men. Justice is now occupied by Christiane Taubira, but, without picture spreads and gossip, her profile is relatively subdued.

Taubira has brought in some admirable anti-harassment legislation, but has already presided over a scandal in which acquittals and lenient sentences followed a protracted gang-rape trial in the Paris suburbs. It led to accusations from feminists that France's soft approach to rapists was symptomatic of a society where the influence of female decision-makers is negligible.

Amel Khadri who works on social projects close to Fontenay-sous-Bois, where the multiple rapes took place, says: "There are too many crimes related to macho men attacking defenseless women. French society seems to show no willingness to tackle these sexist attitudes."

Paris-based feminist activist Anne-Cécile Mailfert says: "Our fight for parity is also about questioning our ability to fight sexist diktats, and the system of male domination, and to construct male-female equality in every field: to recognise the competence of women to exercise power is central and transcends the political sphere."

In 2009, Dati was herself attacked by feminists for returning to work just five days after giving birth. The evidence presented to the Versailles court gives further grist to her detractors' mill as it appears to confirm that much of her time as justice minister was spent pursuing her affair with Desseigne, accompanying him to dinner parties, travelling on holiday to Mauritius – where the pair were inevitably snapped by paparazzi – and that she even considered accepting a "love nest" apartment in Paris's 16th arrondissement from him. Dati is also said to have "burst into tears" when Sarkozy fired her for what many said was an abject inability to be an efficient minister, offering her the relative obscurity of jobs as a Paris mayor and MEP.

This woeful narrative is being picked over by lawyers as Dati puts her all into her potentially life-changing case against Desseigne. For mother and daughter, it could all end in limousines and private planes for life. As far as the profile of French female politicians is concerned, it is another step backwards.

• This article was amended on 27 November 2012. The original said Rachida Dati was France's first female justice minister. She was the first from an ethnic minority.