The government’s controversial NDIS bill will undergo “substantial” amendments after Labor and the Coalition struck a deal, with some of the changes attracting heavy criticism from the Greens, the ACT senator David Pocock and the disability community.

Sixty-three government amendments across both houses will be introduced as part of backroom deals to pass the bill on Tuesday night, the NDIS ministers, Mark Butler and Jenny McAllister, revealed.

Butler said some changes are “relatively technical” while others are “relatively substantial”.

“They will ensure that this bill is the best version it can be,” the minister said.

The bill will go to a vote in the Senate at 8pm where it’s expected to pass with the Coalition’s support.

Among them is a tweak to allow vulnerable participants whose budget is impacted by a new ministerial power – which allows the minister to bluntly slash funding from certain categories across all participants by up to 99% – to apply for more funding through a plan variation.

“We do recognise that there is a need to safeguard against risk to participate in health and safety, particularly for that group of people who require support 24 hours a day,” McAllister said.

“And so we are establishing a new plan variation pathway for people who have high support needs. This is intended to address participants who require continuous care over a 24-hour period. These participants will be able to apply for a plan variation within 90 days of a support determination applying to them.”

The ministerial power to swiftly reduce funding for support categories across all participants has been heavily criticised by both the Greens and ACT senator, David Pocock, as well as the disability community.

In a Tuesday evening debate, Pocock said the change remained the biggest “red line” for him in supporting the bill, describing it as an “indiscriminate cut” impacting hundreds of thousands of participants.

“[In the Senate inquiry], we heard that this will leave people in unsafe situations because it risks isolating them. We know that isolation increases the risks of violence, abuse, and exploitation, and social and community participation is an essential safeguard against this,” Pocock said.

“The indiscriminate nature of this cut means that we will not know its impact until harm happens, and I can’t support that based on what I’ve heard from Canberrans.

“That is something that I cannot support, even though I support the intent of these reforms, minister.”

Steele-John said the changes would impact people with disabilities who require support workers to go into the community.

“This government, in this bill, will be cutting the supports currently available, currently funded, to enable a disabled person to go outside, maybe once or twice a week,” he said.

“The ripple effects of this will be terrible. The stress that it will create is beyond imagining.”

The government estimates the $52bn-a-year scheme will have more than doubled in cost in a decade’s time without intervention. The changes within the bill are expected to instead improve the federal budget’s bottom line by $37.8bn over four years.

McAllister said the government was concerned the fast-rising costs would negatively impact broad support within Australia for the NDIS.

“I don’t think that the community broadly believes that a scheme that costs $100bn a year by the middle of next decade is a scheme that is operating sustainably,” she said.

“But that is the path that we are on, unless sensible amendments are made to the operation of the scheme to ensure that [the NDIS] works as intended.”

The government’s amendment does not exempt any participant from being impacted by the broad funding reductions but it gives those with high support needs a chance to remedy any sudden financial shortfalls from the change.

The Coalition also secured amendments to create new criminal and civil penalties against anyone offering or providing kickbacks using NDIS funding.

Aggravated integrity offences, including obtaining funds by deception, providing false or misleading information, intentionally destroying records and abuse of position as a participant’s nominee will also be introduced.

The government’s plan to pass the NDIS changes this week were almost postponed by the Coalition’s ultimatum to bring tax law changes to close the “widow tax” loophole early.

It was expected that the tax reforms, which include closing the loophole, will be voted on Wednesday morning.