The US organisation Athlete Ally, which aims to support the rights of LGBT sportspeople, has cut ties with tennis champion Martina Navratilova, saying comments she made in a British newspaper were transphobic.
Navratilova -- an 18-time Grand Slam winner -- argued it was "cheating" to allow transgender women to compete in female competition because they would benefit from unfair physical advantages.
Her column written in the Sunday Times newspaper has led Athlete Ally to immediately remove her from their Advisory Board and drop her as an ambassador for the organisation.
In the column Navratilova suggested she would not be happy to compete against a transgender woman and argued a man could reverse their decision after transitioning.
"A man can decide to be female, take hormones if required by whatever sporting organisation 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," Navratilova wrote.
"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."
In a statement released on its website Athlete Ally said Navratilova had perpetuated "dangerous myths" about transgender women.
"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 organisation said.
"As an organisation dedicated to addressing root causes of homophobia and transphobia in and through sport, we will only affiliate with those committed to the same goal, and not those who further misinformation or discrimination in any way. Given this, Navratilova has been removed from our Advisory Board and as an Athlete Ally Ambassador, effective immediately.
"When we launched our Ambassador program in 2011 and invited Martina to join us, we saw her as a trailblazer for LGBTQ people in sports -- someone who, like us, believed in the power of sport to advance equality, dismantle stereotypes, and build a more inclusive society.
"Martina's latest statements stand in stark contrast to that vision, and to our core beliefs and values as an organisation."
Athlete Ally also said it had approached Navratilova previously about "deeply troubling" comments she made referring to transgender athletes on social media, but had not heard back from her when she said she would seek to educate herself further.
Navratilova is yet to respond to Athlete Ally's announcement, but has previously said transgender activists are wrong for denouncing anyone who argues against them.
She also points to her friendship with Renee Richards, the transgender woman who fought to compete in the 1976 U.S. Open after undergoing male-to-female sex reassignment surgery. Richards went on to coach Navratilova to two Wimbledon titles.
Navratilova also campaigns for gay rights after suffering personal abuse when she came out during her career in the 1980s.