A girl of 15 was taken into foster care after she told teachers her parents were refusing to support her decision to change gender.

The family was informed by the deputy head teacher at her school that he was 'powerless to intervene' in preventing them losing their 'much-loved' daughter.

He told them: 'I know she's not a boy but she's self-identified so my hands are tied.'

The case is among those cited by leading professor Michele Moore who warns that children are being taken into care and allowed to change sex at school without their parents' consent.

The 15-year-old, who cannot be identified, complained to the school that her parent were refusing to support her decision to change gender (Stock photo)

She says she is worried about the lack of 'sensible' discussion around children 'self-identifying' as the opposite sex.

And parents, teachers and doctors are unable to question their decision for fear of being branded transphobic, said the expert in inclusive education and disability issues.

Another family told her they only found out their daughter had changed sex and officially registered at her school as male when they visited teachers at a parents' evening.

Earlier this week it was revealed that at least three children were taken into care last year because their parents had objected to them changing gender.

Social workers at Hillingdon council in west London said they placed two children in foster homes following arguments, while Ealing council, also in west London, said it had done the same with 'fewer than five' children. It refused to say exactly how many.

Debbie Hayton, 50, a science teacher in the Midlands, who transitioned from male to female, said: 'Stories like this raise concern that hundreds of children are being pushed into inappropriate and unnecessary treatments that they will later abandon – albeit not without some psychological distress and, potentially, lifelong infertility.

Inclusive Education professor Michele Moore warned there were multiple cases of children going into care in order to transition to the opposite gender without their parents' consent

'There's also the worry many of these children will be suffering from underlying mental health issues, which will not be addressed by gender re-assignment.' Professor Moore, who previously worked at the Patient Safety Academy at Oxford University, claims that there has been a 4,500 per cent rise in girls identifying as transgender over the past decade.

But debate on the reasons for the increase was being shut down by pro-transgender activists and charities, she added, and there was a danger that children were changing gender to be like their peers rather than by individual choice.

A change to an NHS 'memorandum of understanding' last year means that teachers, health workers and GPs are forbidden to explore underlying reasons why a child may wish to change gender – they can only affirm their decision – or face being found guilty of practising 'conversion therapy', resulting in professional sanctions.

But Susie Green, of Mermaids, a charity that supports transgender children and young people and their families, said: 'The young people we see are not puzzled about their gender.

'They are saying, very clearly: 'This is who I am.' The truth is numbers may not have actually increased. Instead, people are making sense of the way they feel earlier and therefore more are seeking help.'