A High Court judge has ruled that a boy who was living life as a girl should be removed from his mother's care.
Mr Justice Hayden said the mother, who cannot be named, had caused "significant emotional harm" to the seven-year-old boy.
The mother described her son as "living in stealth", which was meant that "he was living life entirely as a girl," said Mr Hayden.
"He dressed, at all times, like a girl and, it transpired, had been registered at a new general practitioner's as a girl."
The judge added that he was left in no doubt that the mother was absolutely convinced that her son perceived himself as a girl and that she was fighting for his right to live as such.
The mother had told the judge that the boy "expressed disdain for his penis".
Mr Hayden ordered a review by the council into the care given by Social Services after saying that staff had "moved into wholesale acceptance that the child should be regarded as a girl".
Detail emerged on Friday in a ruling by the judge following private hearings in the Family Division of the High Court in London.
Mr Justice Hayden said no-one involved in the case, including the local authority - could be identified to protect the identity of the child.
The boy is now living with his father who separated from the mother years ago and is described to have settled in well.
The father and his partner were said to be shocked when they first saw the boy by the extent to which he appeared to be a girl, both in appearance and in mannerism.
Mr Justice Hayden said since being removed from his mother's care he has developed a liking for so-called masculine interests, citing children's programmes and an interest in superhearoes as examples.
"I have noted from reports that (the boy) has become interested in Power Rangers, SpongeBob, Superheroes and is constantly finding new interests."
"It is striking that most of (the boy's) interests are male-oriented.
"I am entirely satisfied, both on the basis of the reports and (the father's) evidence at this hearing, that he has brought no pressure on (the boy) to pursue masculine interests.
The father began fighting for access to his son about three years ago after raising concerns about not having contact with his son.
A lower-ranking judge has authorised a "wide-ranging" inquiry into the case and local authority social services staff have begun investigations.