Sixteen teammates of transgender swimmer Lia Thomas on Thursday urged US college sport authorities to follow new USA Swimming rules which could bar her from competing at upcoming championships.
In a letter sent to the University of Pennsylvania and the Ivy League athletic conference by former Olympic swimmer Nancy Hogshead-Makar, the 16 University of Pennsylvania swimmers argue that Thomas should not be allowed to compete in women's competition.
Thomas has dominated US collegiate women's swimming recently as a student athlete at Penn, where just a few years ago, she competed as a man.
Her case has divided opinion, with some arguing she has an unfair physiological advantage while others saying she should be allowed to compete freely as a woman.
On Tuesday, the governing body of swimming in the United States, USA Swimming, unveiled new guidelines which include a more stringent threshold for testosterone.
The new guidelines did not mention Thomas by name, but were widely seen as making it harder for her to be able to compete in major meets such as the Ivy League and National Collegiate Athletic Association championships.
Although some members of the Penn swimming team voiced support for Thomas's right to compete in a statement late Tuesday, a separate faction of the squad on Thursday said she should not be allowed to compete in women's competition.
The names of the 16 Penn swimmers were not included in the letter sent by Hogshead-Makar, the chief executive of Champion Women, a non-profit which provides legal advocacy for girls and women.
The swimmers argued that while they supported Thomas's gender identity, "the biology of sex is a separate issue from someone's gender identity" in sport.
"Biologically, Lia holds an unfair advantage over competition in the women's category," the letter read, noting that Thomas's rankings have surged from 462nd as a male swimmer to 1st as a female.
"If she were to be eligible to compete against us, she could now break Penn, Ivy, and NCAA Women’s Swimming records; feats she could never have done as a male athlete," the swimmers said.
The swimmers added they had been warned that if they spoke out against Thomas, they would be kicked off the team.
"We support Lia's mental health, and we ask Penn and the Ivy League to support ours as well," the letter reads.
"Sport is competitive by definition, and Lia's wins, records, and honors should not come at our expense, the women who have worked their entire lives to earn a spot on the Penn Women's Swimming Team."
The letter urged the University of Pennsylvania and Ivy League not to attempt a legal challenge to the new USA Swimming rules "so that we are able to finish our swimming season with distinction and pride."
Hogshead-Makar and the University of Pennsylvania did not respond to requests for comment.
A spokesperson for the Ivy League said the organization did not comment on letters submitted to the body.