Photos: CNN & University of Pennsylvania

Michael Phelps said sport “has to be a level playing field” when asked about the controversy surrounding Lia Thomas.

Thomas, a transgender swimmer on the women’s team at the University of Pennsylvania, previously spent three years competing on the men’s team.

She has become the topic of debate among those questioning trans participation in sport, with Phelps now weighing in on the topic.

The 36-year-old, who is the most successful and most decorated Olympian of all time, compared the discussion surrounding Thomas to that of doping in sport and stated that he has never competed in a “clean field” in his “entire career”.

“I think this leads back to the organising committees again,” he said in an appearance with CNN’s Christiane Amanpour last week. “Because it has to be a level playing field. I think that’s something that we all need because that’s what sports are. And for me, I don’t know where this is going to go. I don’t know what’s going to happen.”

Phelps, the winner of 13 individual gold medals as an Olympics swimmer, further emphasised his desire for “an even playing field” in swimming.

He continued: “I believe that we all should feel comfortable with who we are in our own skin, but I think sports should all be played on an even playing field.

“I don’t know what that looks like in the future, but it’s hard. It’s a really, honestly, I don’t know what to say. It’s very complicated and you know, this is my sport, this has been my sport my whole entire career, and honestly the one thing I would love is everybody to be able to compete on an even playing field. That’s all I can say.”

Thomas said she avoids getting involved in the debate about her participation and recently told the SwimSwam news site: “It’s not healthy for me to read it and engage with it at all, and so I don’t, and that’s all I’ll say on that.”

Her teammates are also yet to discuss the matter openly.

Current National Collegiate Athletic Association (NCAA) guidelines state that transgender women can compete if they have undergone testosterone suppression for a year.

These are set to be reviewed in 2022, though there has been no indication of them undergoing any changes.