Children under 16 cannot give “informed consent” to puberty blockers, the High Court of England and Wales has ruled, in a landmark decision that campaigners say will deny children with gender dysphoria treatment on the NHS.

The case against the Tavistock Clinic and the NHS Portland Trust was brought by two claimants, 23-year-old Keira Bell, who was prescribed puberty blockers aged 15 and later de-transitioned, and Mrs A, the parent of a trans 15-year-old. 

In a statement, the Tavistock clinic said: “We are disappointed by today’s judgment and we understand that the outcome is likely to cause anxiety for patients and their families”.

Puberty blockers are only prescribed to young people with gender dysphoria after a lengthy medical consultation with a team that will involve a clinical psychologist, child psychotherapist, child and adolescent psychiatrist, a family therapist and a social worker.

The assessment will usually take place over three to six appointments, spaced over several months. Blockers need to be used before puberty in order to effectively pause development in adolescents and are reversible.

The three High Court judges said that the consequences of a later hormone treatment – cross-sex hormones which are irreversible – could not be fully understood and therefore consented to by under-16s, despite this treatment only taking place after puberty blockers and with patients aged 16 or over. As most patients who take puberty blockers then go on to take cross-sex hormones, the judges considered the two treatments a “pathway” that it is “rare for a child to get off.”

Many fear the damage that this could do for young trans people, who are often a highly vulnerable group. One in four trans young people has attempted suicide, according to a 2014 study by charity Youth Chances. 

“I’m terrified,” Alex Vellins, a trans 18-year-old who was treated at the Tavistock Clinic told VICE World News. “I can only think about what waiting for me was like, and it was absolutely awful. It was excruciating.

“We know that being trans and not being able to transition is associated with depression, anxiety and suicide,” he said. “We know that the outcomes of trans people that socially transition are better than those that don’t. If you say that they can’t go on puberty blockers, then they can’t really transition.”

Susie Green, CEO of Mermaids, a charity which supports trans children, condemned the High Court ruling.

“To say this is devastating is an understatement,” she said. “We are seeing panic, desperation and distress on our helpline. This is an unforgivable and shameful betrayal of young people’s rights to autonomy over their own bodies and we are deeply concerned about the impact it will have in the months and years to come.”

Nancy Kelley, chief executive of Stonewall said: “Today’s Court ruling about the prescription of puberty blockers is both deeply concerning and shocking. We’re worried this judgment will have a significant chilling effect on young trans people’s ability to access timely medical support. We welcome the Tavistock & Portman NHS Trust’s stated intention to appeal this ruling.”