Attorney-General Christian Porter also confirmed that employers will legally be able to ask workers to take most of their leave while still receiving the $1500-a-fortnight job subsidy from the government. But workers must be left with their final two weeks' leave and cannot be forced to use that up.

Mr Porter has thrashed out the details of the new JobKeeper program with the Australian Council of Trade Unions.

But he said they had "agreed to disagree on casuals", with the government refusing to budge on its insistence that to qualify for the JobKeeper payment a casual needs to have worked with the same employer for at least 12 months.

A number of non-Australians on working visas will also miss out.

Under the JobKeeper payment, the government is paying a flat $1500-a-fortnight subsidy to all workers in businesses whose revenue has fallen by at least 30 per cent, including part-timers and full-timers, and casuals who have had the same employer for 12 months. The subsidy also goes to not-for-profits whose revenue has fallen 15 per cent, and very big companies with turnover of more than $1 billion if revenue has fallen 50 per cent.

Mr Porter said under the new "JobKeeper enabling stand down" measure, businesses could cut a worker's hours if the worker could not be "usefully employed". But their hourly pay rate could not be changed and they could not be required to work more hours than they were paid for.

The cut in hours must not be unreasonable and would be renewable by the Fair Work Commission, he said. Workers could also seek permission from their employer to get a secondary job in their spare time, he said.

READ MORE:

The legislation to be passed on Wednesday will also allow businesses to change a worker's duties, so long as it is safe and within the skills of the worker and the change is not unreasonable.

Mr Porter said it would be unreasonable for someone to be asked to work "unreasonably far away" from where they live. The measure was designed to allow people to work from home and do duties not normally part of their job, but the changes must be necessary to save the job, he said.

"If the viability of the job is at stake the employer can make the direction," he said.

Businesses will also be able to change a worker's ordinary days of work and require them to use annual leave, as long as they had two weeks' leave still remaining.

Mr Porter said the changes to the Fair Work Act would drive flexibility into the system to save tens of thousands of jobs.

The government's JobKeeper scheme amounted to "$130 billion of life rafts going out to six million Australians whose jobs are on the line", he said.

"It has been a suite of measures designed by the government and we are responsible for that design, but the parliament is responsible for assisting in managing the process by which we send those lifeboats out to those six million Australians," he said.

He had worked closely with the unions and "while I'm not pretending that they love everything in the draft", he had adopted many of the Australian Council of Trade Unions suggestions.

The changes were critical to allow the $1500 job subsidy to flow, he said.

The draft legislation is now with Labor and the other opposition parties, and with employer and other groups before it is released. Labor has said it will not stand in the way.

Our COVID-19 news articles relating to public health and safety are free for anyone to access. However, we depend on subscription revenue to support our journalism. If you are able, please subscribe here. If you are already a subscriber, thank you for your support. If you're looking to stay up to date on COVID-19, you can also sign up for our twice-daily digest here.