Experts say that figure likely understates the true scale of the issue as waiting times for a diagnosis continue to grow.
NHS data shows there were a record 187,567 patients with an open referral for suspected autism in June, with almost 90pc waiting more than 13 weeks for a diagnosis. Many have been waiting more than nine months.
The rapidly rising figures and the associated cost threaten to worsen a council debt crisis. Soaring demand from parents for services have left dozens of local authorities facing bankruptcy within the next 18 months when emergency provisions expire.
Almost £12bn – or a fifth – of the £61.5bn education budget distributed by English local authorities in the last financial year was earmarked for children with Send.
Funding allocated to pupils with special educational needs has risen three times faster than standard funding since the pandemic.
The money goes towards classroom funds, transport for students – such as taxis for pupils who struggle to get to school – and structures in place for administering and supporting claims.
Separate figures published by the County Councils Network (CCN) show that children with autism, social, emotional and mental health needs or speech, language and communication impairments account for 88pc of the total increase in special educational need since 2015, when reforms were rolled out designed to give the parents of children with special needs more control over their education.
Worryingly, the number of children with special needs achieving GCSE-level qualifications has also fallen since lockdown despite the increased spending.
‘The system is broken’
Kate Foale, CCN spokesman for Send, warned that councils faced a £5bn “crisis” in their finances unless urgent action was taken.
She added that parents were becoming increasingly frustrated by an “adversarial” system that is failing parents, councils and taxpayers.
Ms Foale said: “The system is broken. It does not work for families, pupils, nor councils. We are calling for action that includes building new capacity to create inclusion in mainstream schools, alongside moving away from the adversarial nature of the current system.”
In 2015, the Conservative government raised the maximum age at which people could qualify for Send support from 16 to 25 years old, creating an increasing black hole in council budgets.
In 2020 it allowed councils to temporarily keep ballooning deficits on spending for children with special educational needs and disabilities off their balance sheets. This “statutory override” will be in place until 2026.
However, 38 councils with the biggest Send deficits have had to strike deals that give them annual cash in return for austerity plans. Bournemouth, Christchurch and Poole (BCP) Council warned in January that it could face insolvency this year as a result of rising deficits.
A recent CCN survey found that a quarter of respondents said they would be insolvent within a year if the statutory override was removed, with a further quarter saying they would likely go bust within three years.
Separate figures show the number of disabled youngsters in Britain has more than doubled in the past two decades, amid a wave of poor mental health.
Almost 15pc of 11 to 15-year-olds say they have a disability, according to the Office for Budget Responsibility (OBR) and the Department for Work and Pensions (DWP), compared to 6.3pc 20 years ago.
It means this age group is now more likely to be disabled than a typical 35 to 44-year-old was in the early years of this century.
Health services are under growing strain from the combination of the ageing population, worsening ill-health and dire productivity growth, the OBR warned this week.
The crippling cost of Britain’s autism wave
By Szu Ping Chan and Ben Butcher
It was meant to improve children’s lives: the introduction of a new system to support young people with special educational needs and disabilities (Send) in 2014 was designed to give parents more say over their children’s future, as well as enhanced support for their journey into adulthood.
Instead, the combination of increased recognition of conditions like autism and ADHD, a post-pandemic surge in demand and overstretched council budgets has pushed some local authorities to breaking point.
Parents, meanwhile, have been living through a decade of distrust in a system that council leaders admit has become “adversarial”.
Even worse, academic outcomes have gone into reverse.
The crisis at Labour’s doorstep comes even as more money than ever before is being invested in Send.
Local authority spending on children with special needs now totals £12bn, 70pc more than it did before the pandemic.