Following a string of other internal protests, including a speaker refusing to appear alongside her, her invitation was revoked just five days before the event.

Also cancelled was Stephanie Davies-Arai, the director of Transgender Trend, a gender-critical website for parents, after two separate dossiers of allegations were sent to organisers by a trainee doctor and Mermaids, the child trans charity.

In her intervention, Susie Green, the chief executive of Mermaids who was due to speak alongside Ms Davies-Arai and other charities on a panel about support for trans youth, told organisers that Mermaids “cannot be a part of a conference that gives a platform to Transgender Trend, regardless of whether their work is in the public domain or not”.

She went on to tell NHS staff in an email that “in addition to Transgender Trend, I would suggest that CAMHS (child and adolescent mental health services) stay clear of anyone involved with anti-trans pseudo-medical platforms that have been set up with the sole intention of attacking trans people (especially trans youth) and their healthcare.”

Two days before the event, following a late-stage trainee complaint, a GOSH senior leader told Ms Davies-Arai that disinviting her was a “necessary decision to enable the conference to go ahead”, acknowledging they had wanted “thoughtful debate” in “this controversial field”.

Following a flood of complaints from all sides, including through the official NHS whistleblowing policy, it was agreed between GOSH and Health Education England, the national NHS training body, to scrap the conference while a review is undertaken.

The saga has sparked fury from campaigners and the cancelled speakers, just days after the landmark Cass Review published its interim report into NHS gender services which found a “fundamentally different service model is needed”.

‘Slandered, insulted and silenced’

Ms Joyce, whose book was critical of the notion that men and women are merely self-identified genders and not biological, said: “It’s outrageous that a journalist who has written a best-selling book spelling out the harms of this bizarre, evidence-free ideology is no-platformed and subjected to a smear campaign.

“Children are being harmed by gender clinics, and yet when I try to blow the whistle to the child psychiatrists of the future, I’m slandered, insulted and silenced.”

Ms Davies-Arai said it “should concern everyone that the NHS has allowed unsubstantiated claims of ‘transphobia’ to influence their decisions”. She said that given the Cass report, “it is unconscionable of the NHS to continue to silence the voices of those who have always urged caution”.

A spokesman for Great Ormond Street Hospital distanced itself from the event, saying it provided “basic administrative support”, but added: “This is an important and highly complex field, but we can confirm some concerns were raised internally about the programme and we subsequently discussed the issues raised with HEE.”

A Health Education England spokesman said: “Concerns were raised to us through the NHS whistleblowing policy. The event was postponed and we will oversee a review to ensure the rescheduled training meets the needs of all those concerned, including the curriculum for trainees, and the requirements for patient, carer and public involvement.”

Mermaids was contacted for comment.