Malcolm Turnbull is flagging changes to create more flexible workplaces, saying Saturday and Sunday penalty rates are different because of "history".
The Productivity Commission in its draft report recommended Sunday rates for retail and hospitality workers be reduced to match Saturday rates.
"I think over time you will see a move to a more flexible workplace," the prime minister told 3AW radio, noting setting penalty rates was up to the Fair Work Commission.
Opposition Leader Bill Shorten stressed the importance of penalty rates, saying people who work on weekends should be well remunerated.
"Labor believes that people who get penalty rates are not people who are doing the wrong thing," he told reporters in Melbourne.
He denied it was possible to cut penalty rates and have workers not worse off.
Responding to the prime minister's comments about the inevitability of change, Mr Shorten said: "Tony Abbott said on 3AW that WorkChoices was dead, buried and cremated. Malcolm Turnbull today has gone on 3AW and given WorkChoices the kiss of life."
