What do governments need to do this time to avoid pre-NDIS mistakes?

With more than 30 years behind him working in the disability sector, Keith McVilly vividly remembers what life was like prior to the National Disability Insurance Scheme (NDIS).

"State-based services were collapsing under an ever-increasing need to provide services and supports for people with incredibly complex needs. They weren't resourced. They weren't able to keep up," he said.

The NDIS has utterly transformed the way people with disability live their lives, giving them much greater choice and control, and introducing national consistency to what advocates described was a postcode lottery in the old state-run systems.

But at a cost of more than $50 billion this year, it is coming at a growing cost to taxpayers and drawing their ire.

The federal government's dramatic cuts to the NDIS — which is expected to see 160,000 participants removed from the scheme by 2030 — made up by far the biggest single savings measure ($36.2 billion over four years) of this week's federal budget.

The sweeping changes will rely on states and territories — who ran disability services before the NDIS but shut them when the scheme began in 2013 — running supports that do not exist yet, including the Thriving Kids program set to start rolling out in October.

Professor McVilly, now an academic at the University of Melbourne, said he feared a rushed rollout of these new services could undo more than a decade of progress.

"Unless [these] are well designed, we could end up in that crisis situation again."

'Horrendous abuse and neglect'

The 2011 Productivity Commission report that led to the creation of the NDIS found the previous state systems were "underfunded, unfair, fragmented, and inefficient".

At that time, states and territories contributed about two thirds of the overall $7 billion in funding for the disability sector, with the Commonwealth making up the final third.

Governments gave lump sums directly to organisations, who in turn decided who got support and what services would be available. Under the NDIS, participants have much greater choice, and if they do not like what they are getting, can take their money elsewhere.

Jim Simpson, a senior advocate at the Council for Intellectual Disability, who has worked in the sector for decades, described the old system as "a maze with dead end after dead end".

"There were huge waiting lists and services were rationed," he said.

Mr Simpson said people often waited years for essential equipment or housing, only receiving help when they hit crisis point.

"People lived isolated, unsupported lives … often in places like public housing or bleak boarding houses or being homeless."

The availability of supports often fluctuated year-to-year due to state budget cycles, and access to services was heavily dependent on your location and type of disability.

With nowhere else to go, Mr Simpson said people often ended up living permanently in institutions — places where, the disability royal commission heard, shocking abuse, neglect and exploitation occurred.

Professor McVilly's career began as a psychologist in one of these institutions, Hobart's Willow Court, which closed in 2000.

He said he was concerned a move back to block funding could end up leading to more "large-scale residential facilities".

"We know from places such as Willow Court these … facilities leave people open to horrendous abuse and neglect."

A 'really scary' future

Like many of the 760,000 other participants on the NDIS, Sebastian Britos' life today would be very different without it.

Thanks to his NDIS funding, the 20-year-old, who lives with Down syndrome, works two days a week at a day program in Sydney's west, taking staff lunch orders, packing boxes and cleaning the office.

Therapies have built his independence to the point where he can now dress himself, prepare food, clean his room, and help with the washing.

Funding for support workers allows him to go out into the community and to the gym to maintain his health.

"If Seb didn't have access to the NDIS, I think he would be very unhappy … he'd be spending a lot of time in his room watching television and not doing very much," his mother Sabrina Forte said.

Having lived about half his life under the NDIS and half under the old state system, Sabrina said the difference between the two was stark.

She said the group therapies Sebastian had access to before the NDIS were ineffective due to a lack of individual focus on him, and their cost left the family massively out-of-pocket.

"We paid the bills, we paid the mortgage and everything else was on therapy," Sabrina said.

Aside from helping him develop new skills, Sabrina said the NDIS enabled Sebastian to live a full life away from his parents, like anyone else his age.

"He's someone who always needs support, but having the NDIS and having supports that focus on building his capability is essential," she said.

"Anything that takes that away is … really scary for families."

Whatever new supports the states do set up, Sabrina Forte said it was critical they were not a carbon copy of what previously existed.

What needs to happen now?

The federal government has defended its cuts to the scheme as necessary to "save the NDIS from itself" and restore its "social license".

The states have warned they do not have capacity to replace what is being cut, that their new services may not be ready in time and accused the Commonwealth of washing their hands of people with disability.

Professor McVilly said it was not just state services that needed to be rebuilt, but also the way the workforce operated.

He said one benefit of the state systems was the presence of multidisciplinary therapy teams working together, who had extensive qualifications, local knowledge and "understood what it meant to be a person with a disability".

"A lot of the people who in the past provided these services have now been fragmented in the way that they support people," Professor McVilly said.

"They're working as sole practitioners and the NDIS funding mechanisms fund them as sole practitioners."

He said there was next to nothing from the old state systems that could be reactivated and much of their new systems would be starting from scratch.