Trans women retain physique, stamina and strength advantages when competing in female sport, even when they reduce their testosterone levels, new guidelines for transgender participation in national and grassroots sport published by the UK sports councils will say on Thursday. The long-awaited report argues there is no magic solution which balances the inclusion of trans women in female sport while guaranteeing competitive fairness and safety. And, for the first time, it tells sports across Britain that they will have to choose which to prioritise. Stressing that finding new ways to encourage greater inclusion is also hugely important, the report urges national governing bodies to find “innovative and creative ways to ensure nobody is left out” – including coming up with new formats, such as non-contact versions of team sports, that can be played safely and fairly by everyone. “Sport must be a place where everyone can be themselves, where everyone can take part and where everyone is treated with kindness, dignity and respect,” the guidelines state. The landmark report is highly significant because it comes from UK Sport, Sport England, Sport Wales, SportScotland and Sport Northern Ireland, who between them invest hundreds of millions of pounds in sport each year. It also marks a notable change of emphasis, with sports being told they can no longer fudge the complex and nuanced issue of balancing transgender participation with fairness. While the five councils cannot enforce the guidelines, their words carry significant weight and they are likely to be welcomed and implemented by many sports bodies, who have felt in limbo while disputes over how trans athletes participate in sport have raged around them. However, they may face criticism from some women’s advocacy groups, who are likely to argue the guidelines do not go far enough. Conversely, some trans rights groups are likely to voice concerns that the guidelines will lead to trans women being excluded from some sports. Many trans groups are also sceptical of some of the evidence pointing to the advantages retained by trans women in female sport, although the councils say the work is based on exploring almost all of the most up-to-date research in the area internationally. As things stand, most sports follow the guidelines set by the International Olympic Committee in 2015, which permit trans women to compete in female sport if they suppress their testosterone levels below 10nmol per litre. However, in August the IOC admitted these rules were “not fit for purpose” and would be revised in the next few months. The five sports councils across the UK go further still by stating that suppressing testosterone for 12 months “cannot guarantee fairness”. “Rather, there appears to be a retention of physical capacity in transgender people who suppress testosterone from male levels,” it states. “Such physical differences will also impact on safety parameters in sports which are combat, collision or contact in nature.” The guidelines state that because males and females do not often play competitive sports against each other, many people do not appreciate the differences, particularly in team sports. “However, an understanding of the gap between the two sexes can be recognised by results of practice matches between national senior women’s football teams against underage boys’ teams in recent years,” it says. “The national teams from Australia, USA and Brazil were beaten comprehensively (7-0, 5-2, 6-0 respectively) by club teams of 14- and 15-year-old boys.” In reviewing the latest science, the guidelines say adult male athletes have on average a 10-12% performance advantage over female competitors in swimming and running events, and that increases to a 20% advantage in jumping events, and 35% greater performance in strength-based sports such as weightlifting for similar-sized athletes. “The difference in performance, even at the lower range of 10-12%, is not small in terms of competitive outcomes,” they add. “It would result in Adam Peaty being beaten by half the pool length in a short-course 100m breaststroke competition, Dina Asher-Smith by more than 20m in the 200m track sprint, and Sir Mo Farah being lapped twice in the 10,000m track race. “As a result of what the review found, the guidance concludes that the inclusion of transgender people into female sport cannot be balanced regarding transgender inclusion, fairness and safety in gender-affected sport where there is meaningful competition.” The new transgender guidelines are the result of an 18-month review that involved speaking to more than 300 people and 175 organisations, including current and former athletes, transgender people and LGBT+ and women’s groups. It also examined all the latest scientific research, making it the most comprehensive ever report into this hotly disputed area. “No one was able to offer a single solution which would resolve all the identified issues, or that would satisfy all stakeholders,” the review states, before calling for a “reset” in the system. In their report, the sport councils set out 10 “guiding principles” for sports to follow, including acknowledging the fact that categorisation by sex is lawful and that achieving inclusion across all the strands of the Equality Act “is complex and nuanced”. Sports are also given three potential paths they might consider. They are prioritising transgender inclusion; protecting the female category by having open and “female-only” categories; establishing new formats by adapting rules to include non-contact versions of team sports so that everyone can play.