Sia has claimed critics of her new film have “no f***ing idea” after she was accused of ableism over the casting of an autistic character.

The singer/songwriter has made her directorial debut with Music, a musical drama about a young girl with autism named Music (played by Sia’s regular collaborator Maddie Ziegler) who is raised by her drug-dealing older sister (Kate Hudson).

Upon the release of the film’s first trailer, however, a number of individuals on the autism spectrum have condemned Music for casting Ziegler, who does not have autism, in the main role.

“It’s a mighty shame that someone with such a colossal platform is using it to exclude disabled and neuro-diverse actors from their own narratives,” wrote one person. “I’ve been a long-time fan of your work, so this is really disappointing.”

Sia has since hit back at her critics on Twitter, tweeting today (20 November): “Grrrrrrrrrr. F***ity f*** why don’t you watch my film before you judge it? FURY.”

In response to a user who claimed that Sia did not use anyone on the autism spectrum in the film, Sia wrote: “F***ing bulls***. You have no f***ing idea because you weren’t there and haven’t seen the movie.”

Sia argued that she had cast “13 neuroatypical people” and “three trans folk” in the film, “and not as f***ing prostitutes or drug addicts but as doctors, nurses and singers”.

After another person claimed that there are a number of actors on the autism spectrum who would have been more appropriate for the main role in the film, including themselves, Sia replied: “Maybe you’re just a bad actor.”

Responding to the Irish actor Bronagh Waugh, who said the film seemed “pretty offensive”, Sia said that she had originally cast an actor on the autism spectrum to play the main character. She then decided to recast the actor with Ziegler as it would have been “cruel, not kind” to keep them in the film. “She found it extremely stressful and overwhelming,” Sia added.

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In other tweets, Sia argued that the film was inspired by a real-life friend, who she said is neuroatypical, and that two neuroatypical people served as consultants on the set of the film.

“The movie is both a love letter to caregivers and to the autism community,” Sia tweeted. “I believe this movie is beautiful, will create more good than harm and if I’m wrong I’ll pay for it for the rest of my life.”

Music is released on 21 February.