JK Rowling has come out in defence of a woman who lost her job after expressing the view that there are only two biological sexes.
Maya Forstater had tweeted her opposition to government plans to reform gender recognition laws. In one tweet, she said that "men cannot change into women".
In March, she was informed by the charity where she worked, the Centre for Global Development, that her contract would not be renewed.
She took her case to the employment tribunal, arguing that her beliefs should be protected under equality laws.
But an employment judge ruled against her on Wednesday, stating that her tweets were "offensive and exclusionary".
JK Rowling was among those defending Forstater. The Harry Potter author told her 14 million Twitter followers that women should not be forced out of their jobs "for stating that sex is real".
Tweeting with the hashtags "IStandWithMaya" and "ThisIsNotADrill", she said: "Dress however you please. Call yourself whatever you like. Sleep with any consenting adult who'll have you," she wrote. "Live your best life in peace and security. But force women out of their jobs for stating that sex is real?"
Her tweet was met with strong criticism on Twitter, with the Human Rights Campaign saying, "Trans women are women. Trans men are men. Non-binary people are non-binary. CC: JK Rowling."
Forstater has said she is considering her legal options after Wednesday's defeat.
"This judgment removes women's rights and the right to freedom of belief and speech," she said.
"It gives judicial licence for women and men who speak up for objective truth and clear debate to be subject to aggression, bullying, no-platforming and economic punishment.
"I will consider the judgment closely with my legal team to determine what can be done to challenge it."