Scarlett Johansson is facing backlash for her acting choices once again, but has defended her decision to portray a transgender man in an upcoming movie.

The performer, best known for her role as Black Widow in Marvel's Avengers movie franchise, is set to star in Rub & Tug, a film based on the colourful life of Pittsburgh crime boss Dante (Tex) Gill in the 1970s, according to industry media outlets.

A complex, larger-than-life character who built an empire of massage parlours authorities say served as a front for prostitution, Gill died in 2003 at the age of 72. Born a woman, Gill identified as a man and insisted on being addressed as Mr. Gill, according to his obituary.

Johansson will also serve as a producer on the film.

The casting quickly sparked a wave of disapproval online, with many criticizing the filmmakers for not hiring a trans actor to star and decrying the project as another instance of Hollywood sidelining an underrepresented group.

Scarlett Johansson is playing a trans man in her next movie because her ultimate career goal is to take an acting job from a member of each and every marginalized group. —@faithchoyce First the Japanese, and now Scarlett Johansson is taking on the trans community with her new film Rub and Tug. I can't wait until her Rosa Parks film comes out. <a href="https://t.co/nbmoMkoNlN">https://t.co/nbmoMkoNlN</a> —@ValerieComplex Actors who are trans never even get to audition FOR ANYTHING OTHER THAN ROLES OF TRANS CHARACTERS. THATS THE REAL ISSUE. WE CANT EVEN GET IN THE ROOM. Cast actors WHO ARE TRANS as NON TRANS CHARACTERS. I DARE YOU <a href="https://twitter.com/hashtag/RupertSanders?src=hash&ref_src=twsrc%5Etfw">#RupertSanders</a> <a href="https://twitter.com/NewRegency?ref_src=twsrc%5Etfw">@NewRegency</a> <a href="https://twitter.com/hashtag/ScarlettJohansson?src=hash&ref_src=twsrc%5Etfw">#ScarlettJohansson</a> <a href="https://t.co/RkrW8MeGcG">https://t.co/RkrW8MeGcG</a> —@MsJamieClayton

April Reign, the activist behind the #OscarsSoWhite campaign, was among the critics.

"We've seen male and female actors in the past few years walk away from roles so that a person who could bring a more nuanced experience to the character was allowed to shine. That is what should happen here," she wrote.

Just so you don't think I'm bandwagon-hopping, this is me in 2016 talking about Eddie Redmayne, a cis gender actor, playing a trans character. <a href="https://twitter.com/hashtag/OscarsSoWhite?src=hash&ref_src=twsrc%5Etfw">#OscarsSoWhite</a> has always been about all marginalized communities, and allowing those communities to tell their own stories. <a href="https://t.co/6LLExoO4yU">pic.twitter.com/6LLExoO4yU</a> —@ReignOfApril We've seen male & female actors in the past few years walk away from roles so that a person who could bring a more nuanced experience to the character was allowed to shine. That is what should happen here. Rub & Tug isn't your movie, ScarJo. No need to monopolize. <a href="https://twitter.com/hashtag/OscarsSoWhite?src=hash&ref_src=twsrc%5Etfw">#OscarsSoWhite</a> <a href="https://t.co/auwZEeVTtH">pic.twitter.com/auwZEeVTtH</a> —@ReignOfApril

When approached for comment on the backlash, a Johansson representative told online magazine Bustle: "Tell them that they can be directed to Jeffrey Tambor, Jared Leto and Felicity Huffman's reps for comment."

Tambor, Leto and Huffman are cisgender actors who have earned acclaim and awards for portraying trans characters onscreen (in the Amazon series Transparent and the films Dallas Buyers Club and TransAmerica, respectively).

Canadian director Jean-Marc Vallée, who directed Leto in his Oscar-winning role in Dallas Buyers Club, said he doesn't agree with the backlash.

"[It] doesn't mean that because I am casting this type of role that I need to go to this type of person. This is the nature of acting. It's pretending," he said from Montreal on Wednesday.

Vallée said he's open to seeing transgender actors at auditions, but "it's not about aiming for ... an astronaut because your character is an astronaut."

Ghost in the Shell reunion

Rub & Tug will reunite Johansson with Rupert Sanders, who directed her in the controversial live-action adaptation of Ghost in the Shell.

That project came under fire because Johansson played a character that — in the famed original manga series — was a Japanese woman.

Blasted as yet another instance of Hollywood whitewashing, Ghost in the Shell ultimately fared poorly at the box office and received dismal reviews.