NDIS Minister Mark Butler has defended controversial reforms to the scheme, which would involve removing 160,000 people and reassessing all participants, regardless of their disability.
The changes are set to save the NDIS $15 billion annually by the end of the decade, but have prompted criticism from disability groups who fear scheme participants will be left behind without federal support.
Mr Butler said measures to cut the cost of the scheme would be in place long before the first tranche of people were removed in 2028.
"The reductions you'll see in spending don't reflect people coming off the scheme," he told Sky News on Sunday.
"This is going to be a much more efficient, but also effective, way in which to give support to people, frankly, who were never intended to be covered by the NDIS in the first place."
Laws will be introduced to parliament in May to reduce spending growth in the scheme to two per cent each year over the next four years.
National cabinet, which involves federal, state and territory leaders, previously agreed to reduce spending growth on the scheme to eight per cent as NDIS costs swelled, becoming one of the largest items in the federal budget.
The eligibility assessments will be drawn up by a task force and the disability community, but Mr Butler said he expected many people with autism would be removed from the NDIS.
"It really won't matter what condition or disability you have - you will be assessed through a program or through an assessment process that applies equally across the scheme," he said.
"Obviously, given that people with autism are such a big part of the scheme's population, you'd expect them to be a reasonably substantial part of that 160,000."
Mr Butler said the assessments were necessary, despite people on the scheme with severe disabilities having to go through eligibility requirements all over again.
"What we're looking at is the ability of people to function in a day-to-day sense," he said.
"This will be, frankly, much more evidence-based than the diagnosis gateway I've talked about really being the way in which people get onto the scheme."
Prime Minister Anthony Albanese has held talks with Opposition Leader Angus Taylor about the scheme changes.
Opposition assistant NDIS spokesman Henry Pike said the coalition would try to work with the government on the changes.
However, he said he had little confidence the spending growth targets of just two per cent would be met.
"They haven't delivered any of the reforms they've proposed so far, so I've got very little faith they're going to be able to implement what they're promising," he said.
"There's a lot of people outside the scheme who I think deserve support, and there's a lot of people within the scheme who are very deserving, but also some who have much larger packages than they know what to do with."
