Irish Olympian Sonia O'Sullivan says transgender people 'without a doubt' have unfair advantage in sport.
She was speaking after US swimmer Lia Thomas won a 400 yard freestyle relay last week.
Ms Thomas had previously competed on the University of Pennsylvania men's team for three years, before transitioning and moving to the women's team.
But Florida Governor Ron DeSantis refused to recognise her win, and said runner-up Emma Weyant won the event.
Sonia says it's not a fair playing field.
"It's on the fringes of sport at the moment - but it's something that a lot of people are wondering about, if it's something that should be allowed or not in women's sport.
"That a male who becomes a transgender woman, are they allowed to then compete against biological women?
"With the science behind it all, it just doesn't make sense that they should be allowed to do that."
She says men have a different level of ability to women.
"Without a doubt they have an unfair advantage... they take hormones to reduce their testosterone levels, but that's just one factor.
"There's so many other factors in male adults compared to female adults that make them stronger.
"They're at a different level of ability compared to women, that you can't compete.
"When you've already separated the sports into men's and women's sports - then to allow a variable in that the balance is then thrown off - it just doesn't make sense for that to happen, without considering the women who are already in the sport who have been competing and training... throughout their life.
"All of a sudden they've got to face somebody whose just decided - they obviously decide for very personal reasons why they change - but then to also take part in sport, which is for women".
And she says political correctness means we're forgetting other people.
"We're in a world now where everything is politically correct, and we try to say and do things [that are] politically correct.
"But I think sometimes by doing that, we kind of forget the people who were in a position already.
"So it's the nuances that are out there that we adapt to, but we forget about what was there already.
"So why are we not protecting everybody, rather than just protecting the people who are changing."