Caitlyn Jenner has said that trans girls should not be allowed to take part in girls sports at school, describing the issue as "a question of fairness".
The 73-year-old — who is running to become Governor of California — won a gold medal in the decathlon at the 1976 Olympic Games, prior to her own transition.
Asked by TMZ about upcoming legislation which would ban trans athletes from competing in line with their gender identity, Jenner said: "This is a question of fairness. That’s why I oppose biological boys who are trans competing in girls sports in school.
"It just isn’t fair and we have to protect girls sports in our schools."
Jenner refused to answer a follow-up question about whether her views run the risk of "delegitimising the identity" of young athletes who have transitioned.
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Jenner's remarks have been criticised by numerous charities and organisations which advocate for the rights of transgender people.
Eloise Stonborough, associate director for policy and research at LGBT+ charity Stonewall, told Metro that sport should be "open to everyone".
She added: "The reality is that many trans people still feel unwelcome, or even actively excluded from playing sports and no out trans athlete has ever made it to the Olympics.
"For young trans people, this discussion around their right to participate sends a deeply alarming message that they have no place in sport."
UK charity Mermaids, which supports trans and gender non-conforming young people, tweeted that it was "disappointing" to see that Jenner had chosen to "push back against supporting trans inclusion".
Piers Morgan spoke in support of Jenner's comments on Twitter, telling his followers she was "courageous and correct" in her views.
He added that she will now be "destroyed by the trans lobby for stating the obvious".
RuPaul's Drag Race UK contestant Divina De Campo was among those to criticise Jenner on social media.
The drag performer wrote on Twitter: "There is always a section in each community that actively votes against their interests. Jenner is one of those.
"Her track record on LGBTQ people is abysmal. Her talking about keeping people safe is laughable if she wasn't so dangerous. Just another rich old white woman."
Watch: Kris and Caitlyn Jenner have "very respectful" relationship