It calls for the Ministry of Health to "reclassify ADHD/autism as neurodevelopmental disorders and not as mental health disorders", arguing New Zealand's approach to the conditions are "out of date", with "a serious lack of diagnostic support".
The current categorisation of these conditions overloaded the mental health system and stigmatised people with autism and ADHD, the trust argued.
NZ Disability Advisory Trust Disability service navigator Nick Stoneman, who himself has autism, said the ministry claimed not to classify autism and ADHD as mental health conditions, but people with these conditions far too often ended up within the mental health system.
"The diagnosis will say something like that and then the family will have to wait another however many months or years to get a proper assessment."
The trust wanted GPs granted the power to diagnose and prescribe medication for autism and ADHD, with referrals to neurologists rather than into the mental health system, where Stoneman said minimal support was provided.
"It will take it out of mental health totally and stop psychiatrists diagnosing," he said.
"And actually give the power to the family GP to be able to do it – to make the deferral and say it needs to go to a neurologist rather than into mental health"
"That would then free up funding for our people to do our diagnosis, and we do have a number of expert specialists in our field."
The Ministry of Health's Mental health and addiction chief clinical adviser, Arran Culver, said neither autism spectrum disorder (ASD) nor attention deficit hyperactivity disorder (ADHD) were classified as mental health conditions.
The ministry used the International Classification of Disease (the World Health Organisation's ICD 10 and 11) as reference, which classified both ASD and ADHD as neurodevelopmental disorders.
In both conditions people are likely to see a range of health practitioners which could include mental health professionals, he said.
"ASD and ADHD are separate disorders and have separate pathways for diagnosis and treatment, but all services should provide a multidisciplinary, evidence-based treatment response.
"Autistic children are generally referred to child development services or paediatrics/child health services.
"ADHD is diagnosed and treated in a range of specialist environments, including paediatric/child health services, infant child and adolescent mental health services and adult mental health services."
Robin Wynne-Williams had been working as a pediatric practice nurse with ADHD and autism patients for 30 years.
Although autism and ADHD may be officially classified by the ministry as neurodevelopmental conditions, she said the lived experience of people with these conditions suggested otherwise.
Patients were often referred into the mental health system, where they could wait years for a diagnosis.
She also said the DSM 5 (Diagnostic and Statistical Manual of Mental Disorders) - which many New Zealand practitioners may refer to - included a classification of ADHD and autism.
She argued GPs needed to be given the power to diagnose.
"We want ADHD/autism back in proper primary GP care for all the care, diagnosis and authorisation of meds, and also to include the neurologists and general physicians," she said.
The Ministry of Health said they used ICD-10 and not DSM-V, but recognised that clinicians within mental health services may use DSM-V for their own diagnostic purposes.
Wynne-Williams now runs the ADHD information service in Christchurch, providing post-diagnostic information for people and their families – indicating the gap in service available to people with ADHD/autism.
"There is no service in mental health, many psychiatrists do not believe that adults have ADHD, and they know nothing about autism," she said.
"If the system was working there would be no need for my service and no need for the petition."
She said the ministry's response also reflected several key misunderstandings about ADHD and autism, such as the idea that adults cannot have these conditions. For example, the ministry refers to services for children with ADHD while failing to acknowledge its effects on adults.
"Many psychiatrists still think that adults don't have ADD," Wynne-Williams said.
"More than 25,000 patients that I've had, from little kids to big kids [the big kids being adults], I haven't seen too many grow out of it."
Stoneman said the diagnosis of people with ADHD and autism within the health system came with added shame and stigma, and reduced the funds available to the community itself.
"When a diagnosis is done by the mental health system, the mental health system gets the money," he said.
"The money for our community should be governed by us and come to us directly out of the budget.
"We need our kids and our adults diagnosed and we need it done properly the first time, rather than being made to wait."
He also said there was not enough representation of people with autism and ADHD advising the ministry and the Disability Support Service (DSS).
"Parents of kids on the spectrum often advocate very hard for their kids and they forget that the autism and ADHD sector can provide good people," he said.
"I would like to see more engagement, I would like to see the DSS reformed and insist that someone who holds leaderships skills from the ASD community is on that panel.
"It cannot be a parent, it has to be someone with lived experience with being on the spectrum."