The Football Association does not allow mixed football for adults. That's what it'll tell you. But this month a 17-year-old girl was suspended for questioning the presence of a bearded man in the opposing team. That was an offence under the FA's code of conduct because that man says he is a woman.

Since 2013 the FA has allowed male players who identify as transgender into women's teams if they can show they have lowered their testosterone. Three years ago the UK's Sports Councils published transgender inclusion guidance that pointed out that male puberty is not reversible, that testosterone suppression doesn't change that, and that allowing male players into women's teams is neither fair nor safe in a contact sport. Since then the biggest participation sports - athletics, swimming, cycling - have changed their rules to protect the female category, as have many others. But not football, the biggest team sport in the country.

A year after the Sports Councils' guidance, the FA began a policy review. When I spoke to the consultant running the review two years ago, 50 male players had been approved by the FA to play women's football. When we spoke earlier this year there were 72. There is still no public output from the review.

A year ago Telegraph Sport reported on a row that was tearing the Sheffield and Hallamshire women's football league apart. One player, an adult male, was causing havoc. The male ability to shoulder women off the ball, combined with running speed, "made a mockery of the game", one player told me. Other teams withdrew, fearing injury. Privately, one of his team-mates expressed her worry, saying she tried to be on the same side in training so as to avoid his tackles. But she did not dare say so publicly.

This is a recurring theme. A player at the club which reported the 17-year-old told me that she knows it is not right. She claims that a player was tackled so hard by a transgender player that she ended up concussed, and a defender had her shoulder broken trying to block a shot from a transgender player. But she says "there's a culture of fear around discussing this, which means nobody can complain, including opposition players and managers because when they try to bring it up, the local FA has always shut it down."

The Sheffield incident prompted more than 70 MPs and peers to sign a letter to the FA expressing their concern about its policy, and the risk of harm to female players. Earlier this year, in response, senior FA officials met a small group of MPs at Westminster. I was at that meeting, and heard the FA justify its approach on the basis that 72 is a small number in the context of the 2.6 million who play football. This ignores the impact that each one of those 72 has on all the other players in their league.

It's a hidden problem that is only occasionally visible. At Sutton United, a trans-identifying male manager signed a trans-identifying male goalkeeper. After an apparent boycott, the player left. The player whose presence crashed the Sheffield league tried to make a comeback in another team this summer and reportedly did not get FA approval. But stopping one player doesn't solve the problem.

Former FA chairman Lord Triesman has written to the FA chair and chief executive about the suspended 17-year-old girl. Speaking in the House of Lords last week, he said it was shameful, and that he will not let it rest. This weekend hundreds of people protested at the England men's game at Wembley. When Gary Lineker asked on social media for questions for his podcast, The Rest is Football, hundreds replied suggesting he address this issue. So far he has not.

The FA's strategy for women's and girls' football, launched last month, aims to deliver equal opportunities for women and girls to play, with a focus on female health and wellbeing, and safeguarding. It claims to want to grow the game. Then it needs to listen to women. Like the player at the club where the trans player spotted by the 17-year-old plays. She says: "All I want is for the biological differences to be acknowledged, without being told 'Trans women are women' every time anybody raises a question. It's not about rejecting trans people, but about recognising those differences."

The row about male inclusion in women's sport is coming to football. The FA cannot say it wasn't warned. People at the FA know, because they said it themselves. In 2003 when the Gender Recognition Act was being introduced, the FA pointed out that letting male players with trans identities into women's games would make them mixed sex and that "the participation of transgender athletes in their acquitted gender could threaten the fundamental requirement for a 'level playing field' in sport." The people who run the FA know. But do they care?