The rocketing number of children seeking to change sex has become a national scandal, a powerful coalition of whistleblowers, academics and medical experts warns today.

In a dramatic intervention marking a watershed in the transgender debate, they have come together to express fears about the dire consequences faced by thousands of youngsters changing gender – including infertility and long-term health problems.

A whistleblower from Britain's only NHS gender clinic for children said: 'I'm really angry at what's happening to these children. What I've witnessed feels incredibly distressing and disturbing and like something that should be stopped.'

The experts' concerns are laid bare in a forthcoming book of essays entitled Inventing Transgender Children And Young People. It challenges what it calls the 'dangerous' transgender ideology promoted in schools, universities, the NHS and other public institutions.

The rocketing number of children seeking to change sex has become a national scandal, a powerful coalition of whistleblowers, academics and medical experts warns today

Heather Brunskell-Evans, a former research fellow at King's College London, who co-edited the book, said that 30 years ago the thought of a child being born in the wrong body would have made no sense to the public.

She added: 'Now the idea, which was invented by specialists in gender medicine and transgender activists, has become universally accepted.

'But we are collectively arguing that this unquestioning acceptance poses a serious threat to children's well-being and safety. We hope through this book to bring the world's attention to the public scandal of transgendering children.'

The book warns:

Doctors are failing to tell young people they are 'sacrificing' their chance to have children by taking powerful sex-change drugs;

Psychologists are scared to question transgender ideology;

Clinicians who resist diagnosing children as transgender face accusations of transphobia;

Britain's only NHS child gender service is failing to acknowledge other reasons for youngsters wanting to change sex, such as autism;

Teenagers who have 'normal feelings' of discomfort with their bodies are being classified as transgender.

Another contributor to the book, due to be published later this year, is Dr David Bell, consultant psychiatrist at the Tavistock and Portman NHS Foundation Trust in North London, where the NHS child Gender Identity Development Service (GIDS) is based.

Other authors include Professor of Sociology at Oxford University Michael Biggs; psychotherapist Bob Withers, a former senior lecturer at Westminster University; and Dianna Kenny, Professor of Psychology at the University of Sydney, Australia.

Dr Bell, who wrote the book's foreword, called for an 'urgent investigation' into the reasons for the huge rise in the number of gender identity referrals. The latest figures from GIDS show 2,590 children – three quarters of whom were girls – were referred last year. In 2009, the figure was below 100.

The experts' concerns are laid bare in a forthcoming book of essays entitled Inventing Transgender Children And Young People (pictured). It challenges what it calls the 'dangerous' transgender ideology promoted in schools, universities, the NHS and other public institutions

More recently there has been a trend of mainly teenage girls declaring, seemingly out of the blue, that they want to change sex, a phenomenon dubbed rapid onset gender dysphoria.

The Tavistock clinic is the only NHS service for under-18s diagnosed with gender dysphoria, an individual's belief they are trapped in the wrong body.

Dr Bell, a former governor of the Tavistock and Portman NHS Trust, said: 'The rapid escalation of referrals, the large increase in natal [born] females seeking to change gender and the sudden appearance of so-called rapid onset gender dysphoria, cannot be explained by individual factors alone. Nor is it likely to be caused by a large number of individuals feeling free to 'come out' in this new liberal atmosphere.'

The psychiatrist, who last year produced a critical internal report on GIDS which branded the service 'not fit for purpose', further warned: 'Many services have championed the use of medical and surgical intervention with nowhere near sufficient attention to the serious, irreversible damage this can cause and with very disturbingly superficial attitudes to the issue of consent in young children.'

The Mail on Sunday has also seen interviews with whistleblowers who work at the Tavistock clinic, and whose accounts are due to be included in the book. They have chosen to remain anonymous.

The Mail on Sunday has also seen interviews with whistleblowers who work at the Tavistock clinic (pictured), and whose accounts are due to be included in the book. They have chosen to remain anonymous

One of the NHS gender specialists said: 'I keep thinking about all of the children, adolescents and families who are being harmed by the one-dimensional discussion and the attack on truth and on thinking and on what we know about adolescent well-being.'

Another added: 'I'm angry with all the grown-ups, all the clever people, all the thoughtful people, who are letting this happen.' One of the issues causing 'turmoil' at the clinic is the prospect that children are being rendered infertile by the medication prescribed for them.

This newspaper has previously reported that the service has prescribed controversial puberty- blocking drugs to hundreds of children in England, many of whom have been under 14.

The clinicians' damning verdict: Heather Brunskell-Evans, former research fellow at King's College London: 'The idea of a child born in the wrong body, invented by specialists in gender medicine and activists, has become universally accepted. This unquestioning acceptance poses a serious threat to children's well-being.'

'The idea of a child born in the wrong body, invented by specialists in gender medicine and activists, has become universally accepted. This unquestioning acceptance poses a serious threat to children's well-being.' Anonymous NHS child gender clinician: 'There's something really dishonest about the effort going into getting children to preserve their fertility. It would be more honest to say, 'You are almost certainly sacrificing having children.'

'There's something really dishonest about the effort going into getting children to preserve their fertility. It would be more honest to say, 'You are almost certainly sacrificing having children.' Dr David Bell, consultant psychiatrist at the Tavistock and Portman NHS Foundation Trust: 'Many services have championed medical and surgical intervention with nowhere near sufficient attention to the serious, irreversible damage this can cause.' Advertisement

The powerful monthly hormone injections stop the development of sex organs, breasts and body hair.

Young people are advised by GIDS that the treatment is reversible and that if they stop having it, their adult reproductive functions will continue to develop as normal.

But the whistleblowing staff at the service say the drugs – which can permanently weaken bones and stunt growth – put children on an inexorable path to further treatment which is irreversible.

Research has shown the vast majority of those who take puberty blockers go on to start 'cross-sex hormone therapy' at 16, which involves doses of oestrogen for males and testosterone for females. This strong hormone medication begins the physical process of changing individuals from one sex to another and is likely to lead to a loss in fertility.

Yet the concerned clinicians claim the fact puberty blockers are putting youngsters on a pathway to infertility is 'completely swept under the carpet' at the Tavistock. Instead, they say children and teens are being given false hope that they will be able to conceive in the future by being offered the chance by the clinic to freeze their sperm or eggs. In actual fact, it is unlikely they will ever have babies – with boys facing the minefield of finding a surrogate mother to have a baby using their sperm and the relatively low chances of frozen eggs producing a child, the clinicians say.

One GIDS staff member said: 'There's something really dishonest about the effort going into getting children to preserve their fertility. What are we setting them up for? We aren't talking enough about the reality of any blocker or hormone treatment massively reducing the chances of them being able to preserve sperm or eggs. It would be more honest to say, 'you are almost certainly sacrificing having children.' '

At the same time, the gender specialists interviewed for the book raised concerns about children being exposed to physical and psychological harm because Tavistock clinic staff bow to pressure from transgender lobbyists.

They also described how many young people referred to GIDS have suffered homophobic or misogynistic bullying, while some have been victims of sexual abuse.

And as revealed by The Mail on Sunday last year, a third of the young people being referred have clear signs of autism.

Puberty-blocker drugs trial was 'flawed from the start': by Stephen Adams The Tavistock clinic was last night involved in a furious war of words with an Oxford academic who questioned why its medics gave teenagers puberty-blocking drugs in a 'flawed trial'. Writing in the book, Inventing Transgender Children And Young People, Professor Michael Biggs alleges that a Tavistock trial in which 50 children were given the controversial drugs was a 'pretext' for widening access. But the clinic hit back saying the sociologist was not properly qualified to comment, adding: 'We refute these claims, which we consider to be serious, unfair and inaccurate.' Puberty blockers like triptorelin halt physical development by suppressing the release of sex hormones. They are medically licensed to treat 'precocious puberty', where children start developing before the age of 10. However, they have never been licensed in the UK to stop puberty in otherwise healthy, but gender-questioning children. Doctors can prescribe them to such youngsters if they think they will benefit, but 'off-licence' prescribing is usually considered a stop-gap until solid trial-based evidence is available. To that end, in 2010 the clinic started putting teenage patients on the blockers on a trial basis. But Prof Biggs claims, based on examining publicly available data, that medics ignored best scientific practice designed to ensure a fair trial, and then selectively publicised 'positive' results – showing improvements in mental states following blocker treatment – while ignoring 'negative' ones. He also claims an information sheet given to children and parents contained 'incomplete and misleading information' which 'minimised or concealed the risks'. A copy of the sheet obtained by Prof Biggs under Freedom of Information rules claimed children would return to normal sexual development if they came off puberty blockers. It also claimed the drugs 'will not harm your physical or psychological development'. Dr Biggs claims this was an 'astonishing statement' and concludes the trial was 'flawed from the outset'. The Tavistock clinic said it 'categorically refutes' allegations of poor scientific practice such as 'cherry picking' results – and said Prof Biggs' analysis was itself based on 'partial data'. It said: 'The study concluded in early 2019 and we are preparing the dataset. We intend to publish full results in a peer-reviewed journal in line with international best practice.' Advertisement

But Tavistock psychologists are failing to properly investigate whether children are claiming to be transgender because they have an 'autistic obsession', are struggling with being gay or simply have 'normal' teenage feelings of unease with their bodies, the whistleblowers say.

The reason given for this failure is that the clinicians are terrified to question whether a child has gender dysphoria or is actually suffering from other psychological problems for fear of being attacked by trans activists.

They feel they must 'affirm' that the child's problems are primarily about their gender to prevent themselves being accused of being transphobic or trying to practise conversion therapy, it is claimed. They described working in an atmosphere in which 'thinking is shut down, questions aren't allowed and research is never done'.

And they claimed much of the pressure being placed on them to confirm children are transgender comes from influential trans lobby groups such as Mermaids and Gendered Intelligence.

Mermaids – a youth support charity which provides training on gender identity issues to police, NHS workers and Government departments – has attracted controversy for calling for current age restrictions on prescribing cross-sex hormones to children to be scrapped.

Meanwhile, Gendered Intelligence gives seminars on changing gender at schools across the country to pupils as young as four.

The GIDS clinicians said they were equally fearful of the backlash from protective parents, often supported by senior staff members at the Tavistock, if they refused to affirm a child had gender dysphoria or to refer them for treatment.

Other GIDS experts quoted in the book argue that young people who 'self-identify' as transgender are being influenced by external factors such as social media.

And often, these same teenagers idolise YouTube stars such as Alex Bertie who have been credited with making being transgender 'cool'.

However, the clinicians who have spoken out say despite the positive images being projected around changing gender, the future may not be bright for a large percentage of those who decide to do so.

In a chilling insight, one Tavistock specialist said many will face a life-time of health struggles and emotional instability.

She said: 'When you think of children who transitioned at five or even 15, where do you start unpicking that? Where do you start?'

Jay Stewart, chief executive of Gendered Intelligence, said: 'We are extremely disappointed that our professional relationship with the Gender Identity Development Service (GIDS) is being called into question and that the experiences of trans and gender-diverse young people and their families continue to be undermined.

'Any allegation about Gendered Intelligence putting any kind of pressure on clinicians is unfounded. Gendered Intelligence has a professional and respectful relationship with the GIDS team.'

A Mermaids spokesman said: 'We have no control over decisions made by staff at the Tavistock clinic and we do not instruct our service users on what help they should seek within the NHS.

'Our children and young people are often desperate for support and recognition from our hard-working but under-resourced health service and we recognise this can sometimes make it difficult for clinicians.'

Last night a spokesman for GIDS insisted the service took a 'thoughtful and safe approach'. He said an internal review in response to concerns about the clinic's practices had made recommendations to address certain issues.

'However, we strongly refute the blanket and generalised criticisms of the service,' he said.

The spokesman further denied clinicians' claims that GIDS was failing to fully spell out the risks medical treatments being precribed posed to their future fertility. He said: 'The issue of fertility is a complex and developing area. This is always discussed with young people and their families. They can be supported at any point to stop the blocker and pursue fertility preservation.'