The Morrison government last year agreed to introduce extra safeguards at the insistence of commissioner Ronald Sackville and disability advocates, who feared potential witnesses wouldn't come forward unless evidence remained private during and beyond the life of the inquiry.

Mr Sackville wrote to Prime Minister Scott Morrison in February and again in September, pushing for protections similar to those offered to witnesses at the child abuse royal commission.

Among the other protections provided in the bill introduced to the Senate late on Wednesday, penalties of 12 months' imprisonment would apply for the unauthorised disclosure of information.

Compulsory legal requests for information, such as subpoenas, would be blocked, while all records wouldn't enter the open access period under the Archives Act for at least 99 years.

Assistant Minister to the Attorney-General Amanda Stoker, who introduced the bill, said the extra safeguards would mean the commission's findings and recommendations "truly reflected people's experiences".

"The amendments will ensure individuals can have every confidence to come forward and engage fully with the commission without fear that any confidential information they provide may later be disclosed," she said.

Labor this week pressured the government to urgently introduce the laws, arguing delays in introducing protections were undermining the royal commission's work.

Attorney-General Christian Porter in October said he'd ordered his department to "swiftly" draft the amendments, but Wednesday marked the first time details of the changes were revealed.

Thursday is the final day in which both houses of parliament are sitting until May, meaning the legislation would need to be rushed through to avoid further delays.

In a letter to Prime Minister Scott Morrison and acting Attorney-General Michaelia Cash, Labor's Mark Dreyfus and Bill Shorten also described as indefensible the government's decision to last month oppose an alternative set of witness protections put forward by Greens senator Jordon Steele-John.

Mr Steele-John said it was "well about time" the government was acting on the promised changes.

"Coming forward to give evidence about violence, abuse, exploitation or neglect is a very frightening thing, particularly if you are still receiving services from the very people who have abused you or if you are at risk of losing your job if you're identified in the future," he said.

"The royal commission has to be able give disabled people and their families the assurance that they can come forward and tell their stories safely."

The government is still weighing up Mr Sackville's long-standing request for a 17-month extension to the royal commission's reporting timeframe. The report is due in April next year, but Mr Sackville wants the deadline pushed back to September 2023.

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