The report from the Children's Commissioner shows thousands of children with suspected conditions like ADHD, autism, cerebral palsy and a range of mobility and speech, language and communication difficulties are being left without appropriate support for years of their childhoods.

For some suspected conditions, the waits are particularly long to receive either a first appointment or ‘contact', or eventual diagnosis:

• Between referral and a first appointment through Community Health Services, children referred for Down's Syndrome waited the longest - an average of 929 days, equivalent to two years and seven months.

• Children with cerebral palsy faced the highest average wait of 1,222 days to receiving a diagnosis through Community Health Services – equivalent to three years and four months.

• Almost a quarter (23%) of children diagnosed with ADHD waited more than four years after their referral for a diagnosis, while 15% waited more than four years for their diagnosis of autism in Community Health Services.

• Children with intellectual disorders – conditions that impede their learning, judgment, reasoning or problem-solving abilities – waited more than 1,000 days for a diagnosis in Community Health Services.

• Children with tic disorders, including Tourette's Syndrome, experienced waits of more than 800 days to receive a diagnosis.

The waits for the first ‘contact' with services are lengthy through both referral routes but seem to be higher in Community Health Services. The average wait for a diagnosis for any neurodevelopmental condition was two years and three months. Almost half of children (41%, or 14,800) waited over two years for their diagnosis, of which 17% (6,150 children) waited more than four years.

Children from particular groups faced particular disparities, including girls, children from ethnic minorities and children from disadvantaged backgrounds. These groups were often less likely to have their needs identified, exacerbating disparities in access to support.

The data revealed differences in waiting times between regions and even neighbouring areas:

• In Community Health Services, boys make up 70% of children diagnosed with a neurodevelopmental condition. Within specific conditions including ADHD and autism, the gender gap is greater, with girls constituting just 25% and 29% of diagnoses.

• Interviews with children and parents highlighted that where families who can afford to and choose to pay privately for assessment and support, they can access help much quicker than families who cannot afford to.

• In Community Health Services, Asian and black children made up just 1% and 4% of ADHD diagnoses – despite making up 12% and 6% of the child population, respectively.

Children's Commissioner for England Dame Rachel de Souza is calling for solutions that helps move towards a child-focused system led by their individual needs, instead of the current system that relies too heavily on getting a diagnosis before support becomes available, thereby supporting families earlier on and preventing crisis by:

1. Earlier identification of possible neurodevelopmental conditions, and more support in mainstream school including profiling tools being rolled out nationally to prevent overreliance on diagnosis as the silver bullet.

2. A national framework for SEN support in nurseries and schools with a move to a needs-led support system in schools and health services, rather than diagnosis-led.

3. More appointments to tackle the long waits and a joint workforce strategy that covers education, health and social care.

4. A review of children's routes to diagnosis and post-diagnosis support because too many parents feel left isolated and uninformed, even after diagnosis.

5. Better support for families while they await assessment.

Dame Rachel de Souza said: ‘Existing commitments from the government to fix the broken healthcare and SEND systems are warmly welcomed – but now we need urgent action.

‘I'm calling for better support in mainstream schools, improved awareness and training for frontline professionals in education, health and care so that children are supported based on their needs, not a label. We need a system that moves away from a reliance on diagnosis – because failing to provide timely support is robbing children of their childhood and their potential.'

In response, a government spokesperson, said: ‘For too long children and young people with autism, ADHD and other neurological conditions have been let down by a broken NHS.

‘Through our 10-Year Health Plan, this government will tackle this head-on - reducing unacceptable waiting times and improving support before and after a diagnosis.'"We are also committed to improving inclusivity and expertise within mainstream schools, and making sure special schools cater to those with the most complex needs to ensure the best chance life chances for every child.'