Actors union SAG-AFTRA posted a notice to actors, after being alerted by background extras for HBO's upcoming sci-fi series "Westworld" on Tuesday that they were given consent forms asking them to agree to nudity and explicit sexual situations.

HBO has denied approval of the controversial consent form, which has outraged the actors union, celebrities and the public.

"The document that the background actors were given was created by an outside extras casting vendor," HBO said in a statement to Entertainment Weekly. "It was not requested, written or approved by HBO, Warner Bros. Television, or the producers, and contains situations that we do not require of any actor."

Director and actress Rose McGowan was furious about the possible exploitation of young actresses.

"pimps #HBO HELP US @aclu #sag It will be young women getting molested on film for man's profit. WAKEUP," she tweeted early Thursday morning, adding, "#HBO you are putting young women in a hideous position. You are both pimps and johns. And that is a f*cked up thing."

Deadline also reports that more than 50 extras were told they would have to perform simulated sex acts on camera.

SAG-AFTRA told Deadline that the consent form was promulgated by Central Casting. The form said the extras would be required to participate in "genital-to-genital touching" and "oral sex with hand-to-genital touching."

The union claims that HBO knew about the form on Tuesday and refused to do anything about it.

"SAG-AFTRA sent the consent form to HBO [Tuesday] afternoon and requested that the document be changed to more accurately reflect the contractual provisions," a union spokesperson told Deadline. "HBO had every opportunity to rectify this situation, and it was only after their direct refusal to remedy this that we posted the notice on our website. The union is very pleased to hear that HBO is doing the right thing now, but it is disappointing that we had to take such public measures to ensure compliance with our contracts and protect our background actors."

It is unknown if "Westworld's" A-list cast members, including Evan Rachel Wood and Anthony Hopkins, had a similar consent form.

The upcoming "Westworld" TV series is based on Michael Crichton's 1973 film about a futuristic theme park where visitors indulge in dark fantasies with lifelike robots.