Speaking to the committee on Friday, Jodie Griffiths-Cook of the ACT Human Rights Commission warned of a "potential mismatch between the culture" of the National Disability Insurance Agency, which manages the scheme, and the legislation from which it was born.

"Standardised" approaches to support planning were not consistent with the individualised system envisioned in the scheme, she said. At the same time, decisions about how much funding people needed and if they qualified for the NDIS seemed to hang on who happened to be "on the ground running the show" rather than an overarching approach.

"That inconsistency alone speaks to a system that isn't full upholding its obligations," Ms Griffiths-Cook said.

Fourteen organisations and one NDIS participant shared their stories on day one of the inquiry, but while almost all supported the scheme in principle, they also spoke of funding slashed without explanation and children missing out on vital early interventions, of people discharged from hospitals into hotels without suitable housing options or else dragged through the court system, and of others who simply "gave up" and left the scheme altogether.

Lauren O'Brien from the ACT Disability, Aged and Carer Advocacy Service told the story of a client with a psycho-social disability who found the NDIS process so "anxiety-inducing" they ended up in hospital.

Chief executive of the service Fiona May said: "For those with [a mental health condition], the scheme was "making them worse...not better".

A "poster child" for the NDIS, who had benefited from the scheme so much he even did media spots for the agency, found his plan later slashed by 80 per cent.

Lisa Kelly of Carers ACT said there was no explanation and he was left suicidal and eventually hospitalised.

"He thought he had his life sorted, [his mum] thought she could go back to being a mother, all that changed in a heartbeat," Ms Kelly said.

Since the full scheme came into effect in 2016, organisations pointed to a service market failure, particularly for people with high needs requiring therapy or respite care.

Now that the ACT government had withdrawn from the sector, there was no longer a provider of last resort, putting the most vulnerable at risk, the committee heard.

Earlier this year, a Queanbeyan child with complex needs was surrendered to not-for-profit service Marymead because their family could no longer care for them. Chief executive Camilla Rowland said the system didn't know what to do and, within a month, coordinating care for that child had become unworkable.

Ms Kelly said carers were increasingly exhausted and "disrespected" by the new scheme, without appropriate funding for respite that gave them much-needed breaks from caring.

Calls to the organisation's support centre had surged by 60 per cent in the past 18 months alone, she said, and carers were reporting they were now doing about 10 extra hours a week just to coordinate services under the NDIS.

Some had been forced to cut back their work hours or give up their jobs altogether.

"The idea that the NDIS would free carers and enable them to return to work is not being fulfilled and I don't see that changing, I see it getting worse," Ms Kelly said.

The "hyper-individualised" design of the scheme ignored the needs of the family unit as a whole, providers told the committee, especially in cases where more than one member had a disability.

In one case, three children from the same family were spilt up across three different after-school programs, with three different workers and modes of transport, even though they attended the same school and could have been cared for by one worker alone.

Inefficiencies and duplications within the system were common, according to Community Options chief executive Brian Corley.

His organisation provides plan management and helps connect NDIS participants with local services - something NDIS local area coordinators, which work under Feros Care on behalf of the agency, were originally intended to do.

That role had since shifted almost exclusively to planning and reviewing plans, which were then signed off on by the NDIS, the committee heard, meaning the person approving funding for participants was often never in the same room with them.

As organisations spoke of providers chasing unpaid NDIS funds or else closing down altogether, chief executive of Woden Community Service Chris Redmond said the fact the NDIS had had such a detrimental effect on his own multi-service not-for-profit, which was not solely reliant on the scheme, was particularly telling.

While it normally turned over a modest surplus each year to invest back into community programs, this year the organisation was running at a loss and had been forced to cut back on some of those extra services, Mr Redmond said.

"Our viability is at stake."