Former U.S. Rep. Tulsi Gabbard (D-HI) speaks at an "Our Bodies, Our Sports" rally.

Most female athletes support classification by biological sex rather than gender identity in women's contact and endurance sports, in what is believed to be the largest survey on transgender inclusion to date.

58 per cent of the 175 world-class, elite and national-level female athletes agreed with this principle, with the exception of precision sports such as archery. This rose to 77 per cent among those defined as world-class athletes when talking about their own sport. 

However, 81 per cent of all respondents said that the inclusion of transgender athletes needed to be improved, highlighting the difficult balancing act governing bodies face in balancing inclusion with fairness.

The survey, conducted by academics at Swansea University and the Manchester Metropolitan University's Institute of Sport and published in the Journal of Sports Sciences on Wednesday, sought the views of current and former athletes, including 26 world champions, 22 Olympians - two gold, two silver and three bronze medallists - and six Paralympians.

The international federations for athletics, cycling and swimming - three of the most high-profile Olympic sports - now ban anyone who has gone through any part of male puberty from competing in the women's category. US transgender swimmer Lia Thomas is challenging the rules in her sport. Her legal team says World Aquatics' rules are discriminatory.

The study also highlights how opinions vary according to the sport in which an athlete competes, the level at which they compete and the stage of their career. The vast majority of retired athletes (83 per cent) and current Olympic athletes (64 per cent) believe that sports should be categorised according to biological sex.

The percentage was much lower (32%) among athletes from sports whose global federations are recognised by the IOC, but are not currently part of the Summer or Winter Games. "The motivations for world-class athletes to compete in the female category are unlikely to be based on negative actitudes towards transgender people, but rather on a desire for fair competition," the report said.

"These opinions further reflect that transgender inclusion is valued, but fairness for athletes in elite sport must be paramount. It is vital that governing bodies ensure that their policies and committee membership reflect key stakeholders and understand that views vary between athlete groups and sports," it continued.

The reports concluded: "Particular attention needs to be paid to the differences between those with the greatest potential for reward, such as world-class athletes, and those who are not directly affected by policy decisions, such as retired athletes."