Autism groups have expressed shock and disappointment at reports the agency administering the National Disability Insurance Scheme is looking to cut the number of autistic people who are virtually guaranteed of qualifying for support.

Advocates said they believed the National Disability Insurance Agency was working on plans to rein in costs by changing the qualification criteria so that many people would have to be individually assessed to determine their need for support.

The Australian reported on Saturday that the secret plan meant people with the second-most severe of the three recognised categories of autism would no longer be placed on so-called “List A”, which virtually guarantees help under the scheme.

The agency published part of its new plan last week but swiftly removed it and apologised, saying it was a mistake.

Nicole Rogerson, chief executive officer of Autism Awareness Australia, said the government appeared to be backing away from “the commitment to properly fund kids with disabilities” for simple cost-cutting reasons.

“The government are completely under-prepared for how to deal with autistic people under the NDIS but instead of just owning it and saying, ‘We got it wrong,’ they’re just going to cut.”

She said the reported change meant that “if you have level two autism, your family is going to have to make a pretty good case that you need help”.

In the case of young children diagnosed with level two, it was a given that they would need help, Ms Rogerson said. A Productivity Commission report had found more help at an early age saved the system money later, she said.

“It will become this really adversarial system where parents who are already incredibly stressed feel they need to fight the NDIS to get what they really want,” she said.

Katharine Annear, chair of the Autistic Self Advocacy Network, said learning of the apparent plan was “a bit of a shock” and added that the government was not properly engaging with autism advocates.

“It’s a disappointing move but we want to continue to work with the NDIA to define the pathway to support autistic people through a combination of individual packages, funded capacity building and mainstream services,” she said.

“The NDIA does need to have a strategy to bring autism expertise into the agency, especially lived experience of autistic people.”

Of the 142,000 people on the NDIS, 29 per cent have autism.

Social Services Minister Dan Tehan said the agency had not made any changes to the access requirements for autism level two.

“Any person with autism eligible for the NDIS will receive the reasonable and necessary supports they need,” he said.