The mothers, who both have teenager daughters described as “vulnerable” are going to the High Court to force NHSE to guarantee protections.

Both of their daughters are seeking sex-change surgery.

Eighteen per cent of referrals to adult gender services come from 17-year-old patients, court documents have shown.

NHSE has also written to all those of that age who were on the Tavistock waiting list to inform them they will go straight to an adult clinic.

In a witness statement seen by The Telegraph, Dr Neff describes how he is working on the “front line” of transgender care and the “clinical practice in gender-related healthcare is contentious” because as it stands “evidence base is poor and often compromised by serious bias”.

Dr Neff concluded: “In light of the emerging evidence of increasing vulnerability in people attending gender services, and the limitations of the available evidence base, I am not confident that the adult NHS service specifications as written adequately safeguard vulnerable people, or provide treatment or intervention pathways that would be suitable for all.”

LATEST DEVELOPMENTS:

He also argued “a major discrepancy” between the NHSE service for adults and the model of care at his own clinic was that in England there is no “mandated specialist mental-health assessment”.

Anna Castle and another mother referred to as XYZ will launch an appeal for permission to hold a judicial review at London’s High Court on Tuesday.

Castle said: “But it has the least amount of safeguarding and preliminary investigation into whether it is actually necessary and then there is no evidence as to whether it actually helps.

“All these children, all these vulnerable people, as soon as they say they think they are the opposite sex then everyone – institutions, organisations – straight away says that they have gender dysphoria.

“There is no proof of this, they haven’t been assessed. It is frustrating that in any other situation people would be required to give proof of diagnosis.

“But instead society is playing into this assuming that people have gender dysphoria when there are so many other reasons for the troubles that they are having.”