For the last four months, Oxford professor Tariq Ramadan has been rotting in a French jail, like Jean Valjean. He stands accused of rape by several women who came forward during the #MeToo scandal. One says that in a hotel room in Paris in the spring of 2012, the world-renowned Swiss scholar of Islam “choked me so hard that I thought I was going to die”. Another has reportedly described “blows to the face and body, forced sodomy, rape with an object and various humiliations, including being dragged by the hair to the bathtub and urinated on”.

If Ramadan is guilty of these despicable acts, he must face the full weight of French law. But he must first be given the chance to defend himself. And there are grave concerns that he is not.

On 2 February police locked Ramadan up and denied him bail, despite their investigations then being only incipient. They insisted that if they let him go he might flee the country or coerce his accusers into dropping their charges. But Ramadan hardly looked like doing either: he had flown to France to hand himself in and must know that intimidating his alleged victims would ruin his hopes in any trial.

Not only this, but police threw Ramadan into solitary confinement – an indignity usually saved for arch criminals, not mild-mannered Oxford dons. There he has until recently been denied phone calls and visits from his wife and children. A sufferer of multiple sclerosis, he has also reportedly plunged into ill health. He has several times been admitted to hospital; his lawyer says he is enduring migraines, numbness of limb, severe cramp, sleep and memory difficulties; and he now needs support to walk. His lawyer says that a court-appointed doctor in fewer than 20 minutes contradicted the chief prison doctor in declaring him fit for detention. Such failures have provoked the famed French lawyer Régis de Castelnau to call the abandonment of due process in Ramadan’s case “severe and constant”.

Meanwhile, Ramadan is adamant that he is the victim of a smear campaign by his accusers. Last week, the first time Ramadan was allowed to appear before them, judges dismissed the allegations of a fourth claimant. Ramadan’s lawyer called it a “turning point”. The lawyer also cites “inconsistencies, lies and serious doubts” in the accounts of the others. One, Henda Ayari, a feminist campaigner, has changed her testimony of the supposed date and location of Ramadan’s alleged crime. Despite stating that she lost contact with him soon afterwards, she allegedly sent Ramadan sexually explicit messages, seen by investigators, two years later. Another, who is officially anonymous and goes by the name “Christelle”, has explained away apparent contradictions in her account of the timing of the alleged incident by telling judges: “I was drinking rum at this time.”

All this is unusual. Ramadan is not the only man in France accused of rape on the back of #MeToo. Like Ramadan, budget minister Gérald Darmanin and environment minister Nicolas Hulot are the subjects of “mise en garde” – early investigations – into rape and sexual assault allegations by more than one woman. Unlike Ramadan, they await their fate in freedom and, after brief interrogations, have continued to govern. Similarly, David Matthews, father-in-law of Pippa Middleton, who has been accused of raping a minor in France, has been allowed to return to the UK pending enquiries. All three deny their charges.

There appears to be a double standard at work here. And there is too much evidence not to ask whether Ramadan is being treated as he is because he is a Muslim. “Christelle” has been identified as the founder of a website, originally called “Femmes avec Marine [Le Pen]” (“Women with Marine”), which describes violent Muslims assaulting French civilisation. Ayari is an ex-Salafist who last week published a book whose title translates as Never More Veiled, Never Again Raped, She has brought the new celebrity that this case has given her down hard on Muslims, tweeting: “Not all Muslims are anti-Semitic, but most anti-Semitic acts are committed by Muslims!” But she reserves special contempt for Islamists. She has tweeted: “Islamism will not take the place of Nazism! Men and women of peace the world over, regardless of their origins or religions, will unite and they shall be the protective barrier against all hateful Islamists who attack Jews!"

Ramadan does not identify as an Islamist. But he is a prominent Muslim intellectual who insists Islamic and Western values can exist in harmony. A fact so often used against him, his grandfather founded the Islamist Muslim Brotherhood. He rails against Islamophobia in France – where anti-Arab racism is widespread, the burqa is banned and the prison population is 70 per cent Muslim – and he is unflinching in his criticism of the role of the French state in this.

This ruffles feathers. Many powerful figures treat him as a menace who, rather than integrate Islamic and Western values, wants to replace the latter with the former. This is the accusation of Caroline Fourest, a polemicist who once wrote a book called Brother Tariq: The Doublespeak of Tariq Ramadan. Ramadan's defence accuses her of orchestrating the claims against him.

French politicians have been deeply hypocritical in denying Ramadan the presumption of innocence. At the end of January, former prime minister Manuel Valls condemned the “sordid accusations” against the young politician Darmanin. Just two days later, he called Ramadan "an enemy of the Republic and its values, an adversary of what France embodies". He added: "It is up to justice to do its job.” The media have been no better. Among other things, they have repeated the lie that Ramadan is an Egyptian citizen who might escape to North Africa if he is freed.

This political climate might explain certain oddities in the investigation. Why else was Ramadan’s case moved from Rouen, where the initial complaint was filed, to Paris, where the chief prosecutor is François Molins, not an expert in rape but a preeminent counter-terrorist, known by many in France as the “prosecutor of French jihadists”?

Tragically, Ramadan is just the kind of reformist Muslim that President Macron needs. He is part of a generation of moderate Islamic scholars unafraid to challenge the traditionalists who say Muslims cannot be European. I am not suggesting he should be spared justice because of his intellectual credentials. But France claims to have invented liberty. If it fails to uphold its fine ideal now, it will disappoint the world.

That is why I, along with academics, journalists, politicians, scholars and human rights lawyers, have signed a worldwide appeal for Ramadan to receive fair treatment. Britain, where Ramadan lives and to which he has given so much scholarship, must support this call.

Additional reporting by Richard Assheton