A week after appearing on Fox News, Millen appeared again on the network on Tucker Carlson Tonight, reiterating her opposition to the university athlete's inclusion.

She resigned from officiating with USA Swimming after over three decades, with the decision coming a few days before the US Paralympics Swimming National Championships in Greensboro in North Carolina.

University of Pennsylvania's Thomas was not due to compete at these Championships, but Millen said it was in protest of allowing transgender women to compete in women's races.

Millen repeated her opposition in a similar interview on Fox News, but has been criticised for misgendering Thomas.

Misgendering refers to using incorrect pronouns, often used against transgender men and women.

"While Lia Thomas is a child of God, he is a biological male who is competing against women," said Millen.

"And no matter how much testosterone suppression drugs he takes, he will always be a biological male and have the advantage.

"The statement for women then is you do not matter, what you do is not important, and little girls are going to be thrown under the bus by all of this."

Millen went on to say Thomas is "going to be destroying women's swimming", according to Fox News.

Under National Collegiate Athletic Association (NCAA) rules, Thomas is allowed to compete in women's events as she has completed the necessary one year of testosterone suppression treatment.

Thomas competed for two full seasons on the men's team prior to fully transitioning, before switching to the women's this year.

She is now first in the NCAA rankings in the women's 200 metres and 500m freestyle, with the 22-year-old coming close to the collegiate records of US Olympic gold medallists Missy Franklin and Katie Ledecky.