Michael Phelps says controversy surrounding Lia Thomas is 'very complicated,' calls for level playing field

Michael Phelps reacted to the growing debate surrounding University of Pennsylvaniatransgender swimmer Lia Thomas last week, calling the issue "very complicated," while noting that sports need an "even playing field" to be fair. 

Phelps, the most decorated Olympian of all time, compared the controversy surrounding Thomas to doping, saying he doesn’t believe he’s competed in a clean field in his entire career.

"I think this leads back to the organizing committees again," Phelps told CNN’s Christiane Amanpour on Thursday. "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."

Thomas has been dominating the pool in swimming competitions this season. She previously competed for three years on the school’s men’s team, though her success this year ignited criticism over allowing transgender women to compete against biological females.