Sunday penalty rates will be reduced for workers in the hospitality, fast food, retail and pharmacy industries following a decision by the Fair Work Commission.
Full-time and part-time hospitality workers will have their Sunday pay cut from 175% of the usual hourly rate to 150%. There is no cut for casual hospitality staff.
Full-time and part-time "level one" fast food employees will go from 150% to 125%; while casual fast food staff will go from 175% to 150% working on Sundays.
In retail, full-time and part-time employees will go from 200% to 150%, and casual employees from 200% to 175%.
Saturday penalty rates will not change.
Handing down the decision, Fair Work Commission president Iain Ross said the cuts would mean more services and better trading hours on Sundays and public holidays.
He also said the cuts would cause hardship for some and there would need to be transition arrangements.
28-year-old Erin Gibbons, who works as a waitress in Melbourne, told BuzzFeed News she feared the cut will cause uncertainty in the hospitality industry.
"For example, going from a Sunday rate to a Saturday rate might be about $8 an hour. You times that by eight [for a full day] – where are you going to make that payment up?" she said.
"That's where the stress comes from. People will have to look for options, look for means to make up for that cut they've just received."
"It's maybe longer hours, if you can get them. They might have to get a second or third job... the decision can sound so simple, but it has these consequences that are like a domino effect."
The president of the Australian Council of Trade Unions, Ged Kearney, slammed the decision as a "complete furphy" that would create a class of working poor in Australia.
"People whose pay is going to be cut will simply have to work more hours to make up that take-home pay," she said. "You can't survive on a 20% pay cut."
The long-awaited decision comes after a Productivity Commission report handed down in late 2015, which described Sunday penalty rates as "anachronistic".
Prime minister Malcolm Turnbull has said his government would accept the decision of the Fair Work Commission when it came to penalty rate changes.
Minister for employment Michaelia Cash said the decision would lead to longer trading hours, which would benefit the unemployed.
"I have spoken to many employers, in particular in rural and regional Australia, who are unable to open on a Sunday," she said.
"Because of the decision that has been made, they will now be able to be open on a Sunday. That is a good thing, in particular for those who are currently unemployed or who are underemployed."
Labor leader Bill Shorten blamed the Turnbull government for the decision on Twitter.
Shorten has pledged that Labor would ensure workers are not worse off under any changes to penalty rates – potentially by increasing the base rates of pay, or some other kind of compensation.
However, he stopped short at proposing legislation that would guarantee no change to penalty rates.