Fast food, hospitality, retail and pharmacy sectors will begin having their Sunday penalty rates cut with a five percentage point reduction on July 1.
Labor and the unions have stepped up their attack on Malcolm Turnbull as thousands of Australians face a cut to their penalty rates.
A decision by the Fair Work Commission will see Sunday rates drop by five percentage points for workers in fast food, hospitality, retail and pharmacies from this weekend.
While some businesses have committed to not passing on the cuts, the federal opposition and unions claim about 700,000 Australians will be hit.
The ruling comes into effect the same day the deficit levy for those in the highest income tax bracket ends.
"Frankly it's obscene that low-paid workers will be losing real income as a result of the cuts to penalty rates," Labor's employment spokesman Brendan O'Connor told reporters in Melbourne on Saturday.
"Malcolm Turnbull sits on his hands, refusing to understand how difficult it will be for those workers to make ends meet."
Labor has introduced to parliament a private bill to reverse the cuts and has urged the prime minister to support it.
Bill Shorten has vowed reinstate penalty rates if Labor is elected at the next election within the first 100 days of taking office.
"This can be stopped," Mr O'Connor said.
ACTU president Ged Kearney scolded Mr Turnbull for not preventing the cuts and instead choosing to give "very wealthy people" a tax cut.
"While a lot of millionaires go home with more money in their pockets today, workers right around this country are going to be having a pay cut," she said.
Ms Kearney said around 71 per cent of Australians think the measures will make the country less fair, according to union research.
The Shop, Distributive and Allied Employees Association and hospitality union United Voice both lodged an appeal with the Federal Court last week over the Fair Work decision.
The first cut will be five percentage points, with more significant cuts in 2018 and 2019 for fast food and hospitality workers.
Retail and pharmacy workers will have their cuts phased in until 2020.
Public holiday penalty rates will drop 25 percentage points from July 1 for fast food, hospitality, restaurant, retail and pharmacy workers.