Keira Bell, a 23-year-old woman who began taking puberty blockers when she was 16 before “detransitioning”, brought legal action against the Tavistock and Portman NHS Trust, which runs the UK’s only gender identity development service for children.

Kiera Bell, photo by PA - Sam Tobin

The legal challenge was also brought by Mrs A, the mother of a 15-year-old autistic girl who is currently on the waiting list for treatment.

At a hearing in October, their lawyers said children going through puberty are “not capable of properly understanding the nature and effects of hormone blockers”.

They argued that there is “a very high likelihood” that children who start taking hormone blockers will later begin taking cross-sex hormones, which they say cause “irreversible changes”.

In a judgment on Tuesday, Dame Victoria Sharp, sitting with Lord Justice Lewis and Mrs Justice Lieven, said that children under 16 needed to understand “the immediate and long-term consequences of the treatment” to be able to consent to the use of puberty blockers.

The judges said in their ruling: “It is highly unlikely that a child aged 13 or under would be competent to give consent to the administration of puberty blockers.

“It is doubtful that a child aged 14 or 15 could understand and weigh the long-term risks and consequences of the administration of puberty blockers.”

They added: “In respect of young persons aged 16 and over, the legal position is that there is a presumption that they have the ability to consent to medical treatment.

“Given the long-term consequences of the clinical interventions at issue in this case, and given that the treatment is as yet innovative and experimental, we recognise that clinicians may well regard these as cases where the authorisation of the court should be sought prior to commencing the clinical treatment.”