The waiting list for treatment at the only NHS clinic in England to treat gender dysphoria among children and young people has soared during the pandemic.
Figures obtained by the Mail on Sunday reveal that the waiting list at Tavistock and Portman Trust's Gender Identity Development Service (GIDS) in London grew to 5,500 during the pandemic.
It marks a significant jump from the 4,600 cited by the Care Quality Commission (CQC) as being on the waiting list in January 2021.
Commenting on possible reasons for the increase, Stephanie Davies-Arai, founder of campaign group Transgender Trend said: "Life stopped really, so adolescents at that stage in their lives, where they're really searching for their identity, turn online.
"They're bombarded with messages about being trans and that all of their problems and insecurities and anxieties are because they're trans."
GIDS has been criticised by gender-critical campaigners who say that children and young people should not be referred for hormone treatment or puberty blockers.
Earlier this month, an interim report into GIDS by Dr Hilary Cass, former President of the Royal College of Paediatrics and Child Health, concluded that the service was not safe for children and that the level of demand was "unsustainable".
"Because the specialist service has evolved rapidly and organically in response to demand, the clinical approach and overall service design has not been subjected to some of the normal quality controls that are typically applied when new or innovative treatments are introduced," she said.
Dr Cass, who was commissioned by the NHS to investigate services at the clinic, also found that some care providers "are afraid of the consequences" of failing to take an affirmative approach to treating children's gender dysphoria.
"[C]riteria to have accessed therapeutic support prior to starting hormone blocking treatment do not appear to be integral to the current NHS process," the report said.
In January 2021, the CQC rated GIDS "inadequate for being well-led and responsive to patient's needs", and said it "requires improvement for being safe and effective".
Kevin Cleary, CQC's Deputy Chief Inspector of Hospitals, said at the time, "When inspectors visited the Tavistock and Portman NHS Foundation Trust GIDS in October, we identified significant concerns and took enforcement action by imposing conditions on the registration of the trust.
"We fed back our concerns to the trust and also to NHS England and NHS Improvement. We were extremely clear that there were improvements needed in providing person centred care, capacity and consent, safe care and treatment, and governance.