A seven-year-old boy who was "living life entirely as a girl" has been removed from the care of his mum following a ruling by a High Court judge.
Justice Hayden said the woman had caused her son "significant emotional harm" - and he criticised local authority social services staff responsible for the youngster's welfare.
The judge said the woman had been "absolutely convinced" the youngster "perceived himself as a girl" and was determined that he should be a girl.
Justice Hayden said "flares of concern" had been sent from a "whole raft of multi-disciplinary agencies" - and he said he could not understand why so many concerns were "disregarded so summarily" by social services staff.
The judge said social services staff had "moved into wholesale acceptance that (the boy) should be regarded as a girl".
He said he wanted the council to undertake a review of the "social work response" to the case. A council spokesman said bosses had already begun a review.
Detail emerged on Friday in a ruling by the judge following private hearings in the Family Division of the High Court in London.
Justice Hayden said no-one involved in the case - including the local authority - could be identified, and he also barred the woman from revealing specifics of the case in any media interviews.
He said he was afraid that an information jigsaw could be created, which might lead to the boy's identity being revealed.
Family court litigation had started about three years ago after the father, who is separated from the woman, raised concerns about not having contact with his son.
A lower-ranking judge had authorised a "wide-ranging" inquiry and local authority social services staff had begun investigations.
"(His mother) told me that (he) was 'living in stealth' by which was meant, she explained, that he was living life entirely as a girl," said Justice 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: "I was also left in no doubt that (the mother) was absolutely convinced that (the boy) perceived himself as a girl."
Justice Hayden said his "overwhelming impression" was that the woman "believes herself to be to fighting for (her son's) right to express himself as a girl". He said the woman had told him how the boy "expressed disdain for his penis".
Justice Hayden said the boy had settled well in the care of his father - and his father's partner. The youngster still saw his mother.
"I have been told that (the father) and his partner were shocked when they first saw (the boy) by the extent to which he appeared to be a girl, both in appearance and in mannerism," said the judge. "However, what is striking is how well (the boy) has settled down."
The judge added: "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 boy's) interests and energy are entirely self-motivated."