Mila Kunis says that a film producer threatened to end her career after she refused to pose semi-naked.

The star said the man told her she'd "never work" in Hollywood again if she didn't take part in the magazine shoot.

In an open letter published on A Plus, Mila Kunis said she felt "objectified".

"Throughout my career, there have been moments when I have been insulted, sidelined, paid less, creatively ignored, and otherwise diminished based on my gender," she writes.

"I taught myself that to succeed as a woman in this industry I had to play by the rules of the boys' club.

"But the older I got and the longer I worked in this industry, the more I realised that it's [rubbish].

"And, worse, that I was complicit in allowing it to happen."

The 33-year-old actress, who was born in Ukraine, also wrote about another time when she formed a production company with three women.

She claims an "influential male producer" described her as "soon to be Ashton's wife and baby momma" during a chat about it.

"He reduced my value to nothing more than my relationship to a successful man and my ability to bear children," she says.

"It ignored my (and my team's) significant creative and logistical contributions. We withdrew our involvement in the project."

Mila Kunis said that by writing the article, she was making a stand against sexist comments and wanted to talk about gender inequality in the workplace.

"I'm done compromising; even more so, I'm done with being compromised.

"So from this point forward, when I am confronted with one of these comments, subtle or overt, I will address them head on; I will stop in the moment and do my best to educate.

"If this is happening to me, it is happening more aggressively to women everywhere."

She was nominated for best supporting actress at the Golden Globes in 2010 for her role in Black Swan.

Her latest movie was Bad Moms but she's also appeared in Friends with Benefits, Forgetting Sarah Marshall and Date Night.

Mila Kunis and Ashton Kutcher, who married last July, are expecting their second child.

They had a daughter, Wyatt Isabelle, in October 2014.