Ms Bannister wept before an ACT paraliamentary inquiry on Tuesday as she recounted the moment her hopes for the National Disability Insurance Scheme were dashed. They had been high, she said.

Like the other participants of the scheme who shared their stories this week, Ms Bannister backed the sweeping reform to the disability sector that had put individual choice at the heart of support.

But after long delays, cuts to her funding for services and "no transperancy", Ms Bannister said the reality of scheme for her had become starkly different to what was promised.

"I've found the process very disempowering, I've become very depressed and anxious for my future," she said.

"I can't afford to move...I don't want my home to be a hospital."

David Heckendorf, who like Ms Bannister has previously advised the ACT government on the NDIS, said that while the original funding model "wasn't perfect...you were taken care of".

Before states and territories pulled out of the disability sector, there was always someone who knew you, he said, someone who could then talk to service providers on your behalf to come up with "creative solutions" when problems arose.

"[There now] seems to be a real paranoia of opening the flood gates if the NDIA agrees to anything out of the ordinary or...anything that isn't standard," Mr Heckendorf said.

Karna O'Dea has been caring for two adult children with complex autism for decades and said she was frightened now there was no longer a provider of last resort in the ACT. Like many families struggling to provide full-time care, Ms O'Dea admitted she was already considering what will happen when she has to give up her child.

"Stop passing the buck between yourself and the NDIS," she told the ACT committee, urging them to work with the agency to transition adult children with complex needs into supported accomodation.

"A parent I know who relinquished her child said: 'I've relinquished his care because I can't do it anymore, I haven't relinquished my child'."

Last week, it was revealed the National Disability Insurance Agency, which manages the scheme, was considering restricting access to thousands of Australians by rewriting the definition of autism.

Speaking on ABC Radio Canberra ahead of Tuesday's hearing, deputy chief executive at the agency Vicki Rundle did not rule out tightening access requirements for people with autism. Ms O'Dea said the new rules could stop her son accessing supports, even though he required one-on-one care.

Another woman said the "arbitrary" age cut off at 65 for the scheme had left her stranded in the aged care system, which could not provide the support she needed as her multiple sclerosis advanced.

"The NDIS [had] said they would contact us, but when I [eventually] rang up...they said they had no record of me."

By then she had turned 65 and, with what she described as a 'gotcha mentality" on the part of the agency, was denied access to the scheme.

Another woman, who asked not to be identified, said her son had been an early NDIS success story, living independently in his own unit. But when his plan was slashed by 80 per cent, she said it came without explanation and the family was left "devastated".

"The consequences of this were terrifying....We were too frightened to tell our son," she said.

To "claw back" the funding, the family found themselves facing months and months of reviews and "strange conversations" with planners who did not appear to have any understanding of psychosocial disability, she said.

They largely relied on the good will of service providers to get by until funding was restored, including a key support worker who was not paid for five months because of an agency error.

"We can't continue to do this for rest of our lives, we should not have to fight," she said.

Ms Rundle said the scheme was a "massive undertaking" but the board, the agency and the federal government were all confident it could be pulled off with enough support.

Representatives from the agency will front the committee on Tuesday.