The latest NDIS snapshot was published on the same day representatives from the agency behind the scheme fronted an ACT parliamentary inquiry.

Between December 31 and March 31 the total number of people on approved support plans in the ACT fell, as 194 Canberrans left the scheme. In that time, just 115 people joined the NDIS on approved plans.

But those figures also showed about half of NDIS participants in the ACT had not been accessing disability supports before the scheme, Stephanie Gunn from the National Disability Insurance Agency told the inquiry.

That meant the national reform was going "far deeper" than previous state-based models had been able to, Ms Gunn said.

While the agency was hearing positive feedback from many people across Australia, "we absolutely acknowledge that there is much more to do," Ms Gunn said.

One hundred and four people in the ACT unhappy with their NDIS experience had already taken their case to tribunal, she revealed, but agency staff had made a "concerted effort" to reduce the number of plans going to review in the ACT in the past few months.

While the amount of disability service providers in the territory has grown under the NDIS, a number of those organisations, along with advocates, participants and carers, have voiced deep concerns with the scheme's roll-out to the inquiry.

Many reported long delays and huge cuts to support funding, others had been hospitalised due to the stress and "trauma" of the agency's bureaucratic process.

Ms Gunn said all of the stories shared by witnesses to date had already been resolved or were in resolution.

The goal of the NDIS was to deliberately target interventions that would help people "change the nature of the supports they require over time", she stressed, with children in particular expected to leave the scheme after receiving early intervention.

"This is an insurance based scheme, it is not a welfare based scheme," she said.

But committee members, including Canberra Liberal Vicki Dunne and Caroline Le Couteur of the ACT Greens, pushed the agency on reports children in the ACT often weren't getting the interventions they needed because of delays stretching out to six or even 12 months.

This often had a profound clinical impact on a child's condition, Ms Dunne said, leaving them permanently worse off, as in the case of hearing impairment.

Where the agency had "lost [its] way" in the planning process, Ms Gunn said an improved pathway pilot had shown spending more time with families to talk through and review draft plans had led to much better outcomes.

This week, the agency's board is considering the results of that pilot, which was trialled in Victoria.

ACT Minister for Disability Rachel Stephen-Smith acknowleged the work of the agency in improving the scheme but said jursdictions across Australia wanted to see change "sooner rather than later".

In particular, the territory was eager to lead the development of a more tailored pathway model for people with psycho-social disabilities, she said.

In its submission to the inquiry, the ACT government said it was still regularly picking up the cost of service gaps under the NDIS model. One case was costing ACT Health about $300,000 a year to manage, even though the government believed it should fall under the scheme's remit.

In next month's budget, the ACT government has revealed it will give a lifeline to Canberrans falling through the cracks in the NDIS via a new $1.1 million emergency support fund and more staff at the ACT Office of Disability.

Do you know more? Get in touch at sherryn.groch@fairfaxmedia.com.au