(CNN)Tennis great Martina Navratilova has been criticized after claiming it is a form of "cheating" for transgender women to be allowed to compete in women's sport.
The 18-time Grand Slam winner wrote in The Sunday Times that it was "insane" that "hundreds of athletes who have changed gender by declaration and limited hormone treatment have already achieved honors as women that were beyond their capabilities as men."
This is not the first time Navratilova, a gay rights campaigner who suffered homophobic abuse when she came out in 1981, has caused controversy with her remarks on transgender athletes.
In December she was criticized after tweeting: "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 comments led to her becoming embroiled in an online argument with cyclist Rachel McKinnon, the first transgender woman to win a world track cycling title in October 2018.
Navratilova, a nine-time Wimbledon champion, wrote on Sunday that this debate had led to her going away to do more research on the subject, adding: "Well, I've now done that and, if anything, my views have strengthened.
"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.
"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