The states and territories have agreed to support the federal government's overhaul of the National Disability Insurance Scheme (NDIS), putting an end to months of tension.

The federal government's proposal aims to curb spending on the scheme by $14 billion over four years and is expected to pass the Senate this week with Coalition support.

A stand-off between the government and the states and territories had emerged over a plan to shift some NDIS functions back to the states. 

But NDIS Minister Bill Shorten on Wednesday said the government had agreed to a series of amendments to win over the states, including a new dispute resolution approach to escalate issues to premiers and chief ministers and accelerated time frames for changes to NDIS rules.

"Critically, this agreement secures the support of the states and territories for the government's legislation and reform agenda, and will help ensure the scheme is here for the future," Mr Shorten said.

He added that the changes will ensure that the scheme remains sustainable in the "short to medium term".

The states and territories had previously expressed concerns over the speed of the reform, which they said risked "creating service gaps for people with disability" if the services offered under the scheme were changed before the states could establish alternatives.

The reforms give the minister and the National Disability Insurance Agency (NDIA) powers to determine what supports can be accessed with NDIS funding, increase investigative powers and set limits on NDIS participants who seek to top up their plans.

Mr Shorten said he knew there was overcharging and waste occurring within the scheme, but it was difficult to estimate exactly how much.

"Telling the truth about the scheme seems to upset people," he said.

"On one hand, if we say it is changing people's lives, some people will say some should not be getting it.

"On the other hand, when you say there is some waste in the scheme, other people will say you are trashing people with disability.

"The truth is in between."

While the legislation has secured the support of the states and territories, disability groups say they remain deeply concerned.

The national peak body for people with disability, People With Disability Australia, released a statement on Tuesday calling on the government to ditch the bill in its current form, citing a "number of critical concerns".

They included the lack of co-design, increased power for the NDIA, and the need for increased participant rights to review assessments.

The First Peoples Disability Network (FPDN) also called for senators to oppose the legislation in a statement this week. 

"To endorse the bill in its current state is even worse than to accept the status quo and will see to the introduction of wide sweeping, paternalistic and punitive powers that evidence and history tells us will disproportionately impact the lives of First Nations communities," Worimi man and FPDN chief executive Damian Griffis said.

Mr Shorten said he respects the concerns of advocacy groups but described their concerns as "unfounded".

"They know we're fair dinkum ... we've appointed the first ever Indigenous director on the board of the NDIA, Dr Richard Fejo, and there's an amendment to the legislation which will make sure that there is always a presence of a First Nations person on the board."