An Oxford University professor has accused the NHS’s only specialised clinic for transgender children of suppressing negative results while undertaking experimental treatment on adolescents.

Dr Michael Biggs, an associate professor at Oxford’s Department of Sociology claims the Gender Identity Development Service (GIDS) has been giving puberty blocking hormones to children, without robust evidence as to the long-term effects.

It comes after the governor of the clinic based in London with the Tavistock and Portman NHS Foundation Trust resigned last month in protest at its “blinkered” response to doctors who had raised the alarm about “woefully inadequate” care. There is also another centre in Leeds.

Declaring the trial a success, the clinic has continued to treat over a thousand children with the hormones but Dr Biggs’ research suggests that after a year of treatment “a significant increase” was found in patients who had been born female self-reporting to staff that they “deliberately try to hurt or kill myself”.