It is the story of a scandal. For decades a chemical factory pumped toxic waste into a river that led to the sea in southwest Japan, poisoning thousands and leaving children severely disabled.

Now, a director whose forthcoming film tells the story of the Minamata disaster and the work of W Eugene Smith, the photojournalist who documented its devastating legacy, has accused the film studio of attempting to “bury” the project because of the personal problems of its star, Johnny Depp.

Minamata was due to be released in February but has yet to reach the cinemas. A very different kind of toxicity may be to blame.

Depp was dropped from the Fantastic Beasts film franchise last year after he lost a libel case over a tabloid article that called him a “wife-beater”.

His future as a Hollywood star appears in doubt after the High Court judge found that he violently abused his wife, Amber Heard, 12 times. Depp denies the claims and is fighting to restore his reputation.

A scene from Minamata.

When audiences may see his latest film remains uncertain. Andrew Levitas, the director, has written to MGM, protesting about what he claims is a decision to “bury” Minamata. He urged the studio to set aside the negative publicity surrounding the film’s star, claiming that it had a moral duty not to let the actor’s personal problems derail an important story about industrial pollution and corporate cover-up.

In the letter, shared on the Deadline website, Levitas described how the studio bought the rights to the film last year. He wrote: “MGM was intent on bringing to light the suffering of the thousands of victims of one of the most heinous industrial pollution incidents the world has ever seen. In re-exposing their pain in the sharing of their story, this long-marginalized community hoped for only one thing: to lift history from the shadows so that other innocents would never be afflicted as they have … and it seemed in that moment, with MGM’s partnership, a decades-long wish was finally coming true.

The film tells the story of the Minamata disaster and the work of W Eugene Smith, the photojournalist who documented its devastating legacy.

“Imagine the devastation when they learned … that despite an already successful global rollout, MGM had decided to ‘bury the film’ (acquisitions head Mr Sam Wollman’s words) because MGM was concerned about the possibility that the personal issues of an actor could reflect negatively upon them and that from MGM’s perspective the victims and their families were secondary to this.”

The director claimed the studio was refusing to promote the film and would fulfill only its “legal obligation and nothing more.”

Amber Heard arriving at London’s High Court last year.

He wrote: “Yes, you are legally within your rights to bury their story as so many have done before but you have a moral obligation to do better than that.

“We implore you to speak to Mr Uemura [whose daughter was severely disabled as a result of the pollution] and the other victims and offer them the dignity of understanding why you think that an actor’s personal life is more important than their dead children, their siblings, their parents, and all victims of industrial pollution and corporate malfeasance.”

Depp, 58, plays Smith, who, together with his wife at the time, the photojournalist Aileen Mioko Smith, spent three years documenting how the methylmercury that had been dumped by the Chisso Corporation since the early 1950s had contaminated fish and shellfish, which then poisoned people in the Kumamoto Prefecture. It emerged that thousands had been poisoned, including children who were born with deformities.

The couple’s photos were published in Life magazine in 1972 and in a book, Minamata: A Warning to the World.

Neither Levitas nor MGM could be reached for comment. In its response to Deadline, MGM said: “The film was acquired for release via American International Pictures, a division of MGM which handles day-and-date releases. Minamata continues to be among future AIP releases and at this time, the film’s US release date is TBA [to be announced].”

Lucy Bannerman is a reporter and feature writer in London