By Brooke Sopelsa

Athlete Ally, a nonprofit that advocates for LGBTQ inclusion and equality in sports, has severed ties with Martina Navratilova following Sunday's controversial op-ed, in which the tennis star called transgender women who compete in women’s sports “cheats.”

“Athlete Ally unequivocally stands on the side of trans athletes and their right to access and compete in sport free from discrimination,” the organization wrote in a statement. “Martina Navratilova’s recent comments on trans athletes are transphobic, based on a false understanding of science and data, and perpetuate dangerous myths that lead to the ongoing targeting of trans people through discriminatory laws, hateful stereotypes and disproportionate violence.”

The nonprofit then noted that Navratilova has been “removed from our advisory board and as an Athlete Ally ambassador, effective immediately.”

Navratilova, who has been out since 1981 — first as bisexual and later on as a lesbian — took aim at trans women who seek to compete in women’s sports in the op-ed published in this week's Sunday Times.

“Letting men compete as women simply if they change their name and take hormones is unfair,” she wrote. “Simply reducing hormone levels — the prescription most sports have adopted — does not solve the problem.”

“To put the argument at its most basic: a man can decide to be female, take hormones if required by whatever sporting organization is concerned, win everything in sight and perhaps earn a small fortune, and then reverse his decision and go back to making babies if he so desires,” she continued. “It’s insane and it’s cheating. I am happy to address a transgender woman in whatever form she prefers, but I would not be happy to compete against her. It would not be fair.”

This is not the first time Navratilova has made controversial comments regarding transgender women competing in women’s sports. In December, she took to Twitter and wrote, “You can’t just proclaim yourself a female and be able to compete against women. There must be some standards, and having a penis and competing as a woman would not fit that standard.”

Her tweet caught the attention of Canadian Rachel McKinnon, who last October became the first transgender woman to win a world title in track cycling. The two women engaged in a spat on the social media platform, which led to McKinnon calling Navratilova “transphobic” and Navratilova calling McKinnon a “nasty human being.”

At the end of her op-ed, Navratilova took aim at McKinnon again, claiming she and other transgender activists have a "growing tendency" to "denounce anyone who argues against them and to label them all as 'transphobes.'"

“That’s just another form of tyranny,” Navratilova wrote. “I’m relatively tough and was able to stand up for myself in my Twitter exchange with McKinnon, but I worry that others may be cowed into silence or submission.”

McKinnon, who applauded Athlete Ally’s decision to sever ties with Navratilova, called her op-ed in the Sunday Times “disturbing, upsetting, and deeply transphobic.”

"She trades on age-old stereotypes and stigma against trans women, treating us as men just pretending to be real women,” McKinnon said in a statement emailed to NBC News.

"This is an irrational fear of trans women, which is the very definition of transphobia,” McKinnon added. "We do not denounce her comments as transphobic merely because she ‘disagrees' with trans women who support inclusive sport. Her comments are transphobic because they are based on, and perpetuate, an irrational fear and aversion to trans women. And having a trans friend or two does not immunize someone from expressing transphobic views."

FOLLOW NBC OUT ON TWITTER, FACEBOOK & INSTAGRAM