Transgender children as young as 11 will be able to join a controversial puberty blocker trial after regulators watered down their objections.

The launch was dramatically halted in February when the Medicines and Healthcare products Regulatory Agency expressed safety concerns and indicated it wanted to restrict the trial to kids aged 14 and over.

But researchers today revealed they will resume recruitment from August 1 after officials agreed to the lower age threshold.

Furious campaigners will now urge the courts to shut down the 'unethical experiment' by launching a judicial review.

Some 226 kids are due to be given drugs to stop their body’s natural development as part of a trial commissioned by former health secretary Wes Streeting.

He had indefinitely banned the drugs after the Commission on Human Medicines said they posed ‘an unacceptable safety risk’.

But the Labour leadership hopeful backed the Pathways trial into their side-effects, as recommended by the Cass review into the treatment of children who think they are trans.

Campaigners, who want the trial axed completely amid concerns young people could be harmed, said the MHRA appears to have caved in to ‘gender ideology’.

Puberty blockers are hormone-suppressing drugs that pause the physical changes which mark a transition towards adulthood, such as facial hair and periods.

The trial, led by King’s College London, has faced criticism surrounding the ethics of giving children a drug that could cause irreversible harm, including to their brains and fertility.

Helen Joyce, director of advocacy at sex-based rights charity Sex Matters, said: 'It appears that gender ideology has broken yet another institution.

‘The MHRA’s mission is supposedly to “put patients first" in everything it does, and yet it is signing off on a trial that does the opposite.

'It is already clear that puberty blockers are no solution to childhood gender distress, and that they cause unacceptable harm.

'But the MHRA has not only failed to scrap this trial, it has backed away from its earlier concerns and is allowing the trial to go ahead with only trivial changes, such as a minimum age for participants of 11 for girls and 12 for boys.

'Realistically, few if any children younger than that were going to qualify for the trial.

‘And how can such a young child, who has probably been coached in trans ideology online, possibly consent to such serious harms?’

The research was launched following a recommendation by the 2024 Cass Review, which concluded that the quality of research claiming to show the benefits of puberty blockers for youngsters with gender dysphoria was ‘poor’.

Researchers said the UK-wide clinical study aims to provide evidence on how the timing of treatment affects quality of life, mental health, physical development, cognitive function, and gender-related distress.

The trial was originally intended to involve around 226 people aged between 10 and almost 16. The MHRA today confirmed it had agreed a ‘modified protocol’ to the trial, including ‘strengthened safeguards’ such as the introduction of minimum ages of entry.

Researchers from KCL said it had been agreed that birth-registered females must be at least 11 years old while birth-registered males must be at least 12 to take part.

There had previously been no lower age limit, as researchers said ‘good ethical practice dictates that children who are clinically eligible should not be discriminated against on age alone’.

But they said a minimum age limit had now been agreed ‘as we think it is very unlikely that we would recruit young people under this age range’.

In a letter from the MHRA to researchers in February, the regulator expressed concern about the minimum age of participants in the trial, asking for it to be raised to 14.

The letter stated: ‘Since potentially significant and, as yet, unquantified risk of long-term biological harms is present to participants and biological safety has not been definitively demonstrated in this proposed cohort, at the very least, there should be a graded/stepwise approach starting with those aged 14 as the lower limit of eligibility.’

In its update today the MHRA said it had ‘sought the advice of independent experts from the Commission on Human Medicines on participant safety and the adequacy of proposed strengthened safeguards’.

Kate Barker, chief executive of the LGB Alliance, said: ‘It’s shocking that 11-year-olds could be given drugs with lifelong consequences, including permanent infertility.

‘This trial is a mass medical experiment on children, many of whom would grow up to be happily gay or lesbian if left alone.

‘It's especially shameful considering the incredibly weak evidence base for puberty blockers, as noted in the Cass Review.

‘LGB Alliance campaigned successfully against puberty blockers in the NHS and private practice, and we urge [new health secretary] James Murray to halt this trial before more children are irreversibly harmed.’

Legal action is ongoing against the Government and politicians and public figures have expressed their opposition to the trial.

Harry Potter author JK Rowling, who has been outspoken on gender issues, described the trial as ‘an unethical experiment on children who can’t give meaningful consent’.

A campaign group and two individuals are seeking to take legal action against the Health Research Authority (HRA) and the Department of Health and Social Care (DHSC), claiming the ethical approval process for the trial ‘contained serious flaws’.

Researchers said it remains the case that no child can take part without parental consent and added that young people will continue to need to meet all the other eligibility criteria including ‘demonstrating a good understanding of the intervention and its possible benefits and risks’.

No children are expected to be recruited to the trial before August 1, due to the ongoing legal proceedings, the MHRA said.

Researchers from King’s College London said: ‘Our priority remains to safely, and robustly, investigate the benefits and risks of puberty suppression for young people with gender incongruence to improve the evidence base and inform NHS healthcare.

‘We have worked extensively and openly with the MHRA to understand and resolve the questions they raised about Pathways Trial in February, which were not based on the emergence of any new scientific evidence.

‘We have strengthened patient information connected to the trial and introduced a minimum age requirement, however there are no major changes to the design or conduct of Pathways Trial.

‘Approval of the modified protocol paves the way for the study to begin, subject to the ongoing judicial review challenge to the MHRA and HRA’s decisions which focuses on their regulatory processes.

‘As a research team we will engage with this fully and openly.’

Researchers confirmed children and their parents will be given further details about the potential impact of puberty blockers on bone density, and more information on fertility, throughout the trial.

It had already been confirmed that some young people might remain on puberty blockers after the end of their two-year trial, and researchers said they hoped to launch a further study monitoring them.