More than two million workers risk major pay cuts and potentially their jobs under a coalition government, the ACTU says.
The union is worried what will happen if Opposition Leader Tony Abbott, who has flagged a return to non-union workplace agreements, is elected.
Asked how a coalition government would guarantee workers were not screwed over by individually negotiated contracts, Mr Abbott told Fairfax Radio on Tuesday workers were protected by minimum rates of pay.
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But "no minimum hours?" he was asked.
Casuals 'at risk'
"Well, I mean if it suits them and it suits the boss, why shouldn't it be able to happen?" Mr Abbott replied.
It was clear the opposition planned to scrap the requirement for casuals to work a minimum number of hours each week, ACTU president Sharan Burrow said.
"Losing a guarantee of minimum hours of work will put at risk the income and job security of 2.5 million Australian workers who are employed casually," she said in a statement.
"Tony Abbott's plan means employers would be able to call in staff and send them home after as little as half an hour."
Work Choices was being revived, Ms Burrow said.
