The prevailing culture in adult gender clinics is that 'it was up to patients to make their own mistakes', the nation's leading authority on trans issues has warned the NHS.

In a bluntly worded letter to health leaders, Dr Hilary Cass relayed fears raised by medics about rushed consultation processes and a 'clampdown' on offering too many appointments to the same patient.

Specifically, she outlined concerns about patients being given hormone treatment on their second visit – having seen a doctor only once. And she cited claims that at least one psychiatrist provided standard, or 'boilerplate', responses about individual patients' suitability for gender surgery.

Dr Cass's letter was sent to NHS England's directors of specialist commissioning in May, shortly after she delivered her landmark review on care for trans children.

The full extent of her concerns about adult gender clinics is only emerging now. Her intervention came after doctors who had worked in the clinics approached her to describe their experiences.

Referring in the letter to discussions she had had with these fellow medical professionals, Dr Cass wrote: 'The most common concern was the very limited time for assessment and the expectation that patients would be put on hormones by their second visit.

'In most instances, the individuals described a first appointment with a non-medical practitioner who was not necessarily clinically trained, and usually a medical practitioner seeing patients at the second visit.

'One clinician told me they would be subject to complaints if they delayed putting patients on hormones and another told me their practice was monitored and if they offered a patient too many appointments this was 'clamped down on'.'

Dr Cass also relayed testimony that one psychiatrist was 'providing 'boilerplate' letters which do not reliably reflect the individual patient under consideration'. But Dr Cass's most damning verdict was on the culture that persisted in the clinics.

She continued: 'There was a perception from some [clinicians] that the approach was ideologically driven and polarised and it was difficult to question the approach or discuss concerns.

'Clinicians described a philosophy that it was up to patients to make their own mistakes.'

Maya Forstater, of human-rights charity Sex Matters, said: 'Adults who believe that they can change sex often have complex mental-health histories and are in the grip of 'magical thinking.' '

Health and Social Care Secretary Wes Streeting said: 'I am pleased to be working with NHS England to fully implement the recommendations from Dr Cass's review.'