The federal government's centrepiece industrial relations legislation appears set to pass parliament this week, with support secured from key crossbench senator David Pocock.

Its bill will encourage new multi-employer pay deals, targeting sectors such as childcare which, the government argues, will help push wages up.

However, the bill is opposed by some major employer groups, who argue the changes will burden businesses with lengthy and complex negotiations and increase the likelihood of industrial action.

Employment Minister Tony Burke said he had been involved in long-running talks with Senator Pocock and had agreed to some key changes to the bill to ensure his support.

"He would have preferred that everything was dealt with next year, when we said we wanted to make decisions this year," he said.

"It's involved a very intense process, a lot of meetings and a lot of detail."

Those changes aim to ensure smaller businesses are not unfairly wrapped into agreements that are not suitable for them, and an annual review of support payments such as JobSeeker.

The government expects to be able to pass the bill with the support of the Greens and Senator Pocock.

Senator Pocock said that, with the changes in place, he was comfortable voting it through sooner than he would have liked.

"This is now a substantially different bill to the one introduced in the House of Representatives a month ago," he said.

"It is better for business, better for workers and makes sure the most-vulnerable in our community are no longer left behind."

This week's sitting of federal parliament will be extended to Saturday to ensure the bill passes before the end of the year.

Key changes to get bill over the line

Mr Burke said the government had made three key changes to the bill to secure Senator Pocock's support, with the deal only brokered late on Saturday night.

Two are fairly technical changes to the legislation, and the third actually sits outside of this particular bill altogether.

The government will agree to all recommendations from a Senate inquiry into the bill, including a provision to exclude businesses with fewer than 20 employees from the single-interest bargaining stream, rather than the previous threshold of 15 employees.

That single-interest stream is the path which will allow pay deals to be brokered across a range of similar businesses, the most controversial aspect of the bill.

Another tweak will assist businesses with fewer than 50 employees to argue to be excluded from such agreements, requiring unions to prove the businesses should be covered, rather than the other way around.

The second change will give the minister a specific power to designate an occupation or industry that will be eligible for the "supported" bargaining stream, which differs from the single-interest stream and is designed to cover workers in low-paid industries.

Finally, the third change sits outside the scope of these laws but could be consequential for people on government support payments such as JobSeeker.

An independent panel will be established every year to review the level of support payments — such as JobSeeker — ahead of each federal budget.

That advice to the government will have to be published at least a fortnight before the budget is handed down.

Senator Pocock said he was happy with the changes, and the new review of support payments was a "game-changer" for those living below the poverty line.

"I went into this seeking to get the best policy outcome, balancing the urgent need for workers to get a pay rise, with legislation that will work in practice by delivering pay rises for those that need it while not placing unreasonable burdens on small businesses," he said.

"I believe we have achieved the right balance, significantly improving the legislation with the added commitment that will help stop governments leaving our most-vulnerable behind."

Questioned on whether the government would consider lifting JobSeeker, Prime Minister Anthony Albanese said the government is always looking to take those sorts of steps – but it is not always possible.

"There's more I would like to do," he said.

"We do have fiscal constraints, and we do have to make sure any action of the government bears in mind inflation and the economic circumstances that are there."

Coalition and business groups urge government to wait

Key business groups are maintaining their opposition to the legislation, despite the changes announced this morning.

The Australian Chamber of Commerce and Industry argues the changes are not enough to ease their primary concerns, that businesses could be forced into unsuitable agreements, and the cost of negotiating agreements will be enormous.

Chief executive Andrew McKellar said the bill simply won't do what the government says it will.

"The Bill, as it stands, will do nothing to achieve the aim of increasing wages, and will only add cost and complexity to Australian businesses at a time when they are dealing with deteriorating conditions," he said.

Shadow Minister for Employment Michaelia Cash said the government should be heeding such warnings.

"When the employers in Australia, despite the deal that has been struck, stand up and say this bill will not achieve its stated purpose, but worse than that, have a detrimental impact on the Australian economy, I have one last plea for Mr Albanese," she said.

"And that is, please listen to the job creators in this country."

Greens will also back bill

The Greens have also agreed to support the bill, saying they had secured changes to protect low-paid workers and parents.

They said they were largely happy with the bill, but had concerns around changes to the "better off overall test" (BOOT).

The Greens said they had secured changes meaning future employees would continue to be covered by the test when new agreements were considered by the Fair Work Commission.

And, they said, they had secured an enforceable right for parents to request unpaid parental leave.

Greens leader Adam Bandt said the BOOT change was an important protection for low-paid workers.

"This is an important win for all workers, especially low-paid workers in the retail and the hospitality industries," Mr Bandt said.

Unions have warmly welcomed news the bill is set to pass.

ACTU Secretary Sally McManus said the legislation will provide a fairer platform, for workers to negotiate the pay rises they need.

"This bill gives working people the hope and the opportunity to be able to be on a more equal platform to be able to negotiate fair pay rises and fair workplaces," she said.