Sunday and public holiday penalty rates for workers in the fast-food, retail, hospitality and pharmacy sectors will drop 10 to 15 per cent.
Pharmacy staff will be among the worst affected workers, losing more than $3200 a year, when penalty rate cuts hit on Sunday.
The Fair Work Commission cut Sunday penalty rates for hospitality, retail, pharmacy and fast food employees from July 1 last year.
Fair Work said that penalties for some industries should be reduced each July, with changes starting last year and continuing until 2020.
The next change applies from 1 July 2018. The extent of the changes depend on the industry, with penalties to be reduced by 10 or 15 per cent.
The decision was backed by the Federal Court, after a union challenge, but a Senate inquiry report last October called for it to be overturned.
The Turnbull government rejected the proposal, accepting the independent umpire's call.
Labor's employment spokesman Brendan O'Connor said the government had rejected eight opportunities in parliament to protect penalty rates.
"Last week, millionaires got a $7000 tax cut. This Sunday, workers' penalty rates will be cut again," he said.
According to Labor's figures, pharmacy workers will take a cut of $3,273.73, while retail staff will lose $2,450.81 and hospitality workers $1,884.37.
There is also a $1,628.85 a year hit to fast food workers and $586.05 for those working in restaurants.
