Tennis great Martina Navratilova, a gay rights advocate, has faced criticism for a column she penned in a U.K. newspaper where she claimed that allowing transgender women to compete in women’s sporting events is insane and “cheating.”

Navratilova wrote the column in The Independent newspaper in response to fallout from a tweet from December that read, “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.”