The footballer Megan Rapinoe has become the highest profile sportswoman to publicly support transgender athletes competing in women's competition, arguing that the debate is about something much bigger than sport.

Rapinoe, who is a World Cup winner and Olympic champion with the United States, also suggested that there was minimal evidence to show that transgender women had distorted elite competition since they were included in most women's sports, subject to suppressed testosterone levels.

"I'm 100 per cent supportive of trans inclusion," Rapinoe told Time magazine. "We're missing almost everything. At the highest level, there is regulation. In collegiate sports, there is regulation. And at the Olympic and professional level. It's not like it's a free-for-all where everyone's just doing whatever.

"I think people also need to understand that sports is not the most important thing in life, right? Life is the most important thing in life. And so much of this trans inclusion argument has been put through the extremely tiny lens of elite sports. We're talking about kids. We're talking about people's lives."

Fina, world swimming's governing body, ruled over the weekened that transgender athletes who had reached male puberty could no longer compete in elite women's sport. It had previously been possible provided that they had suppressed their testosterone to below 5nmol/L for a continuous year. Under those rules, the American swimmer Lia Thomas became the first openly transgender athlete to win an NCAA Division I national championship after winning the women's 500-yard freestyle event in March.

No transgender athlete got close to winning a medal at the Tokyo Olympics, but scientists have reported that transgender athletes do retain significant physical advantages after puberty even if testosterone has been suppressed. This was the basis for the decision in swimming and they have now proposed a new 'open' category in which transgender women could compete. No precise details have been released and it remains unclear whether there would be sufficient numbers for meaningfully competitive events.

Fina's new rules do not currently apply below international events and individual governing bodies must still formulate their own policy.

Rapinoe urged wider consideration of the overall impact on transgender people of new rules, especially at a grassroots level. "We're talking about the entire state government coming down on one child in some states, three children in some states," she said. "They are committing suicide, because they are being told that they're gross and different and evil and sinful and they can't play sports with their friends that they grew up with. I think it's monstrous. I would also encourage everyone out there who is afraid someone's going to have an unfair advantage over their kid to really take a step back and think what are we actually talking about here. Your kid's high school volleyball team just isn't that important. It's not more important than any one kid's life."

Rapinoe believes that the starting point should be inclusion. "Show me the evidence that trans women are taking everyone's scholarships, are dominating in every sport, are winning every title," she said. "I'm sorry, it's just not happening. So we need to start from inclusion, period. We can't start at the opposite. That is cruel. And frankly, it's just disgusting."

Fina president Husain Al-Musallam said that swimming's new policy was "based on real science" and there is confidence that it will prove robust against any legal challenge in being "necessary and proportionate to achieve a legitimate" objective. "Our athletes must come first," said Al-Musallam. "Of course I understand why transgender athletes would like to compete in a category of their choice. However, I have an obligation to every single one of our athletes. Equality is also a key principle for us. This is why we are faced with such a delicate balancing act. We have to protect competitive fairness, and also the past records and achievements."

Dr Seema Patel, senior lecturer in Law at Nottingham Law School, however, said that sports were failing to protect the human rights of transgender people. "There has been a continued reliance on inconclusive scientific evidence concerning performance advantage and athletic ability, which tends to obscure what is at stake here," she said. "The rights of trans athletes, including their dignity, integrity, privacy and protection from discrimination, are equally paramount when drawing competitive lines.

"Sports bodies are currently failing to effectively protect the human rights of gender diverse [trans female and athletes with sex variations] athletes in sport. There is a panic that is being created around performance and advantage, which is diverting attention from the human rights issues in this debate. This leaves minority groups such as gender diverse athletes, in a vulnerable position."