Sen. Tommy Tuberville questioned why women's rights groups aren't fighting to keep transgender athletes out of women's sports in order to maintain an even playing field.

Debate around whether transgender women should be allowed to compete against biological females escalated in recent months as Lia Thomas excelled in collegiate swimming. The University of Pennsylvania swimmer, who competed as a male for three years, became the first transgender athlete to win an NCAA Division I title this month.

"Where are the women’s rights people?" Tuberville said during a Fox News interview. "Where are the feminist groups that fought tooth and nail for Title IX?"

NCSS Lia Thomas

Lia Thomas of the University of Pennsylvania stands on the podium after winning the 500-yard freestyle as other medalists, from left, Emma Weyant, Erica Sullivan and Brooke Forde, pose for a photo at the NCAA Division I Women's Swimming and Diving Championship on March 17, 2022, in Atlanta, Georgia. (Justin Casterline/Getty Images)

Title IX, part of the Education Amendments of 1972, forbids sex-based discrimination in federally funded education programs, including athletics.

NBC NEWS MUM AFTER BEING ACCUSED OF EDITING IMAGE OF TRANSGENDER SWIMMER LIA THOMAS

Tuberville, a former Auburn University head coach, said Title IX was "one of the best things that the federal government has ever done, especially for women and building leadership for women, from young girls on up."

Fox News previously reached out to several women's advocacy groups about their position on transgender athletes, but none responded. (In a separate interview with Fox News Digital, Champion Women CEO Nancy Hogshead-Makar spoke out on the issue.)

"What you look for in sports is fairness," Tuberville, an Alabama Republican, told Fox News. "We started Title IX to give women the same level playing field as men."

He said he "can see great harm" if transgender women are allowed to continue competing in women's athletics. 

"You're going to see downfall of young girls getting into sports at an earlier age," Tuberville told Fox News. "They're not going to have the opportunities."

Sen. Tommy Tuberville

Sen. Tommy Tuberville speaks during a Senate Health, Education, Labor, and Pensions committee hearing in Washington on Feb. 25, 2021. (Caroline Brehman/Pool via Reuters)

Tuberville cosponsored the Protection of Women and Girls in Sports Act, which would limit women's sports at federally funded athletic programs to biological females.

"If you’re going to play in sports, you go by your biological gender, how you were born," Tuberville told Fox News. "We have a men’s league. We have a women’s league."

"If you want to have a transgender [league], I’m fine with that," the senator continued. "I think everybody should have the opportunity to compete."

Tuberville pointed to the size difference between Thomas and her competitors.

"You got to have a level playing field," he said. "And there’s just not a level playing field when you allow somebody that’s that much bigger, faster, stronger, and there’s nothing you can do to change that."

NCAA rules previously allowed transgender women to compete alongside biological females after taking testosterone suppression medication for at least 12 months. Thomas had exceeded this requirement, though the NCAA has since changed its rules to allow the national governing body for each sport to create their own eligibility requirements.

But even with hormone therapy, an athlete who went through puberty as a male will still have size advantages, according to Mayo Clinic physiologist Dr. Michael Joyner.

"Height's probably not reversible, hand size, foot size. Some of the issues related to muscle mass, lung size, and other things probably are never gonna revert completely, if at all," he told CBS News.

Thomas' supporters have said the swimmer should be able to compete with biological women, anyway.

The Human Rights Campaign, for example, said the NCAA has "repeatedly failed to take responsibility for ensuring that safe environment in fact exists for LGBTQ+ athletes, women, and athletes of color."

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Meanwhile, Supreme Court nominee Ketanji Brown Jackson wouldn't define what a woman was during a confirmation hearing last week.

Supreme Court nominee Judge Ketanji Brown Jackson is sworn in for her confirmation hearing before the Senate Judiciary Committee Monday, March 21, 2022, on Capitol Hill in Washington. (AP Photo/Jacquelyn Martin)

Supreme Court nominee Judge Ketanji Brown Jackson is sworn in for her confirmation hearing on March 21, 2022, on Capitol Hill. (AP Photo/Jacquelyn Martin)

She should have had "a lot better answer than ‘I’m not a biologist,’" Tuberville told Fox News.

The Alabama senator said he plans to question Jackson about Title IX and the rules around transgender athletes when he meets with the Supreme Court nominee ahead of her confirmation vote. Tuberville expects the issue to eventually make its way to the high court.