Labor and the Greens say the government needs to act to stop penalty rate cuts rather than launch a fresh attack on union-employer deals.
Malcolm Turnbull will on Wednesday bring to parliament tough new penalties to crack down on union misconduct, recommended 14 months ago by a royal commission.
Secret payments between employers and unions that could have a corrupting influence or were not made with a legitimate purpose in mind will be outlawed.
As well, employers and unions must publicly disclose any payments that flow from the employer to the union at the time of an enterprise agreement.
But Labor says the government should instead focus on the 700,000 workers in the retail, hospitality, fast food and pharmacy sectors who are soon to lose some of their penalty rates.
Labor and the Greens have introduced private bills to stop the Fair Work Commission's decision from being implemented and want a vote on them as soon as possible.
Labor leader Bill Shorten says it's a "straightforward choice".
"You can either vote to save the Sunday pay rates of young people, of women, of people in the regions, of workers who depend upon these penalty rates ... or vote to endorse cutting them," he says.
Mr Turnbull says Mr Shorten sacrificed penalty rates as a former Australian Workers' Union leader doing deals with companies.
Workplace issues are expected to be discussed in the coalition and Labor party room meetings in Canberra on Tuesday.