The family of a Pulitzer-winning playwright has filed a copyright infringement lawsuit against Guillermo del Toro and Fox Searchlight alleging that the Oscar-nominated film The Shape of Water is a “derivative” work that has “glaring similarities” to a 1969 play.

David Zindel, son of American playwright Paul Zindel, filed the complaint Wednesday alleging that Del Toro’s critically acclaimed film, which has more Oscar nominations than any other this year, has “exploited” the play Let Me Hear You Whisper and should have credited and licensed his father’s work.

The allegations, which Del Toro and the studio have denied, were first reported in the Guardian in January. The copyright complaint filed in California this week marks the first legal action the Zindel family has taken against The Shape of Water, which is nominated for 13 Oscars, including best picture, best director, best original screenplay and three acting awards.

The suit, filed less than two weeks before the Academy Awards on 4 March, outlines similarities in concept, characters, themes and plot points. The Shape of Water, co-written by Del Toro and Vanessa Taylor, tells the story of a 1960s Baltimore laboratory cleaner who falls in love with a sea creature whom she tries to rescue. Let Me Hear You Whisper, which aired as a TV production nearly 50 years ago, is also about a female janitor in a laboratory who bonds with a sea creature whom she attempts to save.

“The [film] tells a story that is substantially similar, and in many ways identical, to that of the play,” Zindel’s lawyers wrote in the complaint, alleging “overwhelming similarities” that are “too egregious to ignore”.

The complaint – which seeks damages and references the film’s earnings of more than $70m at the box office – notes that both works take place during the 1960s during the cold war in a secret laboratory that conducts experiments for military purposes. Both protagonists are unmarried and introverted cleaning women who work graveyard shifts at the labs, the suit continues, adding that there are parallel characters, including a co-worker friend, their supervisor, a scientist and the aquatic creature.

In both stories, scientists are studying the creature’s advanced abilities for military applications and use electrodes to incite reactions. Both works use a motif of a “romantic vintage song playing on a record player inside the laboratory”, the suit says. Both women also share their lunches with the creature, dance with a mop to flirt with the animal and try to rescue it when the lab makes plans to “vivisect” the creature. The cleaners both use a laundry cart in their rescue plans and aim to release the creature to the sea.

The suit further alleged that both works adopt a similar “dreamy” and “surreal” mood and rely on “fantasy sequences” of the main character.

The works do have substantially different endings, and The Shape of Water has an important male character who does not resemble anyone in the play.

David Zindel said in a statement to the Guardian on Wednesday that the “troubling matter was brought up with Fox five weeks ago but was met with inertia”, adding: “The glaring similarities between the film and our father’s play are too extensive for us to ignore and so we had to act.”

The complaint was also filed against the novelist Daniel Kraus, an associate producer who has been credited with creating the “original idea” for The Shape of Water alongside Del Toro.

Kraus, who did not respond to a request for comment, said in a recent interview that he came up with the idea when he was 15 years old, which was around the time of a 1990 television production of Zindel’s play, the suit noted. The complaint also alleged that Kraus was “well aware of Zindel and admired his work”, pointing to a recent article by Kraus listing Zindel’s 1968 book The Pigman as among the best young adult books of all time.

Fox Searchlight said in a statement to the Guardian: “These claims from Mr Zindel’s estate are baseless, wholly without merit and we will be filing a motion to dismiss. Furthermore, the estate’s complaint seems timed to coincide with the Academy Award voting cycle in order to pressure our studio to quickly settle. Instead, we will vigorously defend ourselves and, by extension, this groundbreaking and original film.”

Paul Zindel, who died in 2003, won the 1971 drama Pulitzer for the play The Effect of Gamma Rays on Man-in-the-Moon Marigolds.

In its original statement last month in response to David Zindel’s claims, the studio said Del Toro had “never read nor seen Mr Zindel’s play in any form”, adding that the film-maker “has had a 25-year career during which he has made 10 feature films and has always been very open about acknowledging his influences”.

