In a speech to the ACT parliament, Ms Davidson said the federal government had shifted its values on the program.

The federal government has expressed alarm over the rising costs of the program and has sought to slash cost by introducing mandatory independent assessments.

But Ms Davidson, who has been highly critical of the proposed reforms, said new federal NDIS Minister Linda Reynolds, who was moved into the role in March, was too focused on the costs of the scheme.

''Federal minister Linda Reynolds' language is focused on the costs of the system, not the value of everyone being able to participate in our community and live an ordinary life," she said.

"This isn't the NDIS, we Australians, signed up for. It isn't the NDIS that this ACT government signed up for on behalf of our community."

Ms Davidson said the "financial sustainability" of the scheme dominated conversations between the states and territories and was the focus of reviews and "razor gang taskforces".

Policy was happening on the run, Ms Davidson claimed, and there was a lack of collaboration and consultation.

"Public policy is occurring on the run and playing out in the media and social media. This is no substitute for collaboration and co-design," she said.

The federal government has claimed the scheme has ballooned above expectations.

Tuesday's budget showed the annual cost of the NDIS was set to nudge above $30 billion in the next three years, which was $5 billion above forecasts made just seven months ago.

But the revised projections were not significantly higher than the Productivity Commission's estimates.

"The 2017 Productivity Commission estimate of costs by 2024-25 was $30.6 billion," Ms Davidson said.

"While the federal government have been throwing some big talk around about $13.2 billion of extra funding in the federal budget, they have in fact committed to only an additional $1.3 billion in 2024-25 over the Productivity Commission estimates for 2024-25, to a total of $31.9 billion in funding for supports.

"This is not unexpected, particularly as the system matures and we develop a better understanding of what it needed, I am not fooled by federal government's smoke and mirrors."

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Ms Davidson also said the government's pre-pandemic surplus was due to an underspend on the scheme.

"The federal budget is underpinned by a $4.6 billion structural underspend on the NDIS that brought the budget back into surplus in 2018-19, prior to the pandemic," she said.

"It is unacceptable that people with disabilities not receiving support is the reason we had a surplus as we went into the pandemic in 2020, and that is the reason the budget is not in an even worse deficit today.

"That is a travesty and the federal government should be ashamed."

It is not the first time Ms Davidson has spoken out against the federal government's proposed changes.

Ms Davidson has strongly advocated for the federal government to abandon its proposed trial of independent assessments for NDIS participants.

Reforms to make the independent assessments permanent were put on hold last month with Ms Reynolds saying she would not make a decision on the new regime until the results of an ongoing trial has been assessed.

In response to Ms Davidson's comments, Ms Reynolds said she was holding discussions with state and territory ministers around the changes, which she said were needed to give participants more control over how they live their lives.

"I am having continued, genuine and frank discussions with the sector, participants and families on a fairer NDIS. I'm also engaging closely with state and territory ministers," Ms Reynolds said.

"We are meeting again in July to work through the independent assessment feedback and the outcomes of the second independent assessment trial before bringing forward legislative changes.

"There is so much to be celebrated with the NDIS as a world first scheme. However, as the legislation has not been significantly amended since it was introduced in 2013 there are improvements we can and must make."

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