Emerald Fennell has revealed details about her “primal, sexual” adaptation of Wuthering Heights, following controversy over the film’s casting choices, erotic trailer and “aggressively provocative” screen tests.

Speaking publicly about the film for the first time at Brontë Women’s Writing festival over the weekend, the Oscar-winning Saltburn director said Emily Brontë’s twisted classic “cracked me open” after reading it at 14 years old.

“I’ve been obsessed. I’ve been driven mad by this book,” she said. “I know that if somebody else made it, I’d be furious. It’s very personal material for everyone. It’s very illicit. The way we relate to the characters is very private.”

Fennell said her first adolescent experience of the novel inspired her approach to the sex-charged retelling of Catherine Earnshaw and orphan Heathcliff’s relationship, set on the moors of 18th-century Yorkshire. “It’s an emotional response to something. It’s primal, sexual,” she said.

Fennell added: “[It is] an act of extreme masochism to try and make a film of something that means this much to you. There’s an enormous amount of sado-masochism in this book. There’s a reason people were deeply shocked by it.” Working on it has been “a kind of masochistic exercise”, she said, “because I love it so much, and it can’t love me back, and I have to live with that”.

The production has received backlash for the casting of Margot Robbie as Catherine and Jacob Elordi as Heathcliff, with critics calling for a Black actor to play the latter character, described in the book as having dark hair, dark eyes and dark skin.

Fennell explained her decisions, recalling the moment she “wanted to scream” when she saw Elordi with sideburns on the Saltburn set, as he reminded her of Dirk Bogarde and “looked exactly like the illustration of Heathcliff on the first book that I read”.

Robbie, she continued, is “not like anyone I’ve ever met and I think that’s what I felt like with Cathy”. Describing the wily protagonist as a “sadist” who “likes to pinch you”, Fennell added that Robbie is “the type of person who, like Cathy, could get away with anything. I think honestly she could commit a killing spree and nobody would mind.”

“It needed somebody like Margot … somebody who has a power, an otherworldly power, a godlike power, that means people lose their minds.”

Kharmel Cochrane, the film’s casting director, previously defended the choices, saying there is “no need to be accurate” as the source material is “just a book”.

Fennell also confirmed that, as with many other adaptations, the film will only focus on the first half of the book and not continue the story after Cathy’s death. She added that “an enormous amount of dialogue is verbatim” because “I couldn’t better it, and who could?”

For the sceptics, Fennell said that part of the novel’s enduring power is that “no one is in agreement about any element of it”, and she added: “I can’t make something for everyone.”