A parliamentary review into Australia's disability support scheme has been told that the practice - while not commonplace - takes place across the country.
The WA-based South West Autism Network has documented more than 20 examples of surprise visits from authorities that have followed National Disability Insurance Scheme assessments.
"They just knock on the door without warning, saying they're from child protection and there's been a complaint," the group's chief executive Nick Avery told AAP.
The allegations - denied by the National Disability Insurance Agency, which administers the scheme - come amid a tightening of support services which have left many families fearful and frustrated.
Ms Avery recently told senators that parents who outlined concerns about their ability to support their autistic children had been targeted.
"When they query large funding cuts, they're being told 'that's parental responsibility (and) if you can't perform your parental responsibilities we'll have to contact child protection and family support'," she said.
"NDIS staff are following through on that threat ... simply because the parents are asking for more support for their child."
Similar experiences were documented anonymously at the royal commission into the treatment of disabled Australians, which ended in 2023.
"When I lost my NDIS supports, I couldn't keep up with everything," one person wrote.
"Then I got a call saying there had been a report to child protection. It was like they were waiting for me to fail."
The same royal commission found the child-protection system often punished parents with disability for systemic failures that were not their fault.
According to the autism network, based on known cases, the visits failed to produce interventions because "there was no evidence of violence, abuse, neglect, nothing".
"We have heard from both child protection staff and from families affected by this that the investigator was quite annoyed to have this family reported with no evidence," Ms Avery said.
Families involved - which span at least WA, NSW and SA - are reluctant to talk about their experiences, even anonymously, due to fear of retribution.
A WA Department of Communities spokesman said the agency investigated child safety matters when there were wellbeing concerns linked to potential neglect or abuse.
An NDIA spokesman said that complaining about NDIS funding would not result in a referral.
"Child protection referrals occur only where there are child safety concerns that meet relevant legal and policy thresholds," a statement to AAP said.
The government plans to move tens of thousands of people with autism - the largest cohort receiving NDIS support - off the scheme each year to 2030 to ease budgetary pressures.
At $51 billion, the NDIS was the second-most expensive program in last year's federal budget, behind only the aged pension.
Recent cutbacks to the scheme include halving support given to "social and community participation" and a 10 per cent cut to services like speech therapy.
Decisions for each family come down to all-important assessments, often undertaken by agency staff via phone call.
Children and Young People with Disability Australia (CYDA) says that process can be terrifying.
"CYDA continues to raise concerns about the experience many families face when interacting with the very systems that are designed to support them," acting chief executive Liz Hudson said.
"The evidence is clear. Governments cannot say they do not know what families are experiencing."
The community services sector has opposed the NDIS cuts, which were codified in August when related laws passed with support from the coalition.
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