After three surgeries for brain cancer, Ms Mamalai lives with the ongoing effects of those surgeries, and is unable to drive.

"The NDIS gives me the freedom to be a mum and a normal person," Ms Mamalai said.

But in July last year the agency in charge of the national disability insurance scheme made the decision to stop participants from using money assigned to them as "core supports" for their transport needs.

Previously if a participant had used all of their assigned transport budget, they could choose to use funds left in their core support budget for transport. Now if the transport budget has been used, participants face paying out of their own pocket even if there are unused funds in their plan.

Canberra woman Ms Mamalai has been able to use the supports to attend events at her children's school, and to attend meetings in Sydney for the Australian Brain Cancer Mission.

Attendance at more meetings this year could be in jeopardy without the ability to use core support funding to pay for a support worker to travel with Ms Malamai as well.

"I don't understand why this change has happened," she said.

Bill Aldcroft from QuestCare in Canberra said he knows of many disability support providers that are set to be tens of thousands of dollars out of pocket because services they have offered under the previous interpretation now need to be paid for by the participants themselves.

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Disability service providers face telling their clients they can't help them, or offering the service knowing it's unlikely they will be paid. Many are choosing the latter, Mr Aldcroft said.

One organisation that asked not to be identified said they will be owed $100,000 by their clients by the end of the year for services the NDIS previously funded.

"They continue to charge the clients knowing that they're not going to get the money back," Mr Aldcroft said, explaining that providers didn't want to leave their clients in the lurch.

A bipartisan parliamentary committee recommended reversing the change in December, but the government is yet to respond to the report. An independent review released this week recommended more flexibility and transparency in how decisions are made.

Labor has accused the government of making the change to protect the thin budget surplus, after a $4.6 billion underspend on the NDIS contributed to bringing the budget back into balance.

"You have to question, is this actually about the surplus?" said Canberra Labor MP Alicia Payne.

"Is this about this government maintaining a surplus that is based on underspending the NDIS?"

A spokesman for the minister responsible for the NDIS Stuart Robert refuted that claim.

"The NDIS is a demand-driven and uncapped scheme," the spokesman said.

"Claims of the government deliberately directing the NDIA to cut NDIS plans are false and are unnecessarily creating fear for participants."