Bill Shorten will bring to parliament on Monday a private bill to reverse the cuts to penalty rates.
The Labor leader says the government needs to come clean on whether it would oppose Sunday penalty cuts for workers covered by modern awards in the retail, hospitality, fast food and pharmacy sectors.
The parliament's bipartisan selection committee signed off on Mr Shorten presenting the private member's bill when it last met.
The Greens' Adam Bandt has also been approved to present his own bill along the same lines.
The legislative moves come as the government rejected a media report plans were under way to launch a public information and advertising campaign in favour of the penalty rate cuts.
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A spokesman for Special Minister of State Scott Ryan said there was no proposal for such advertising.
Mr Shorten said the government could not be trusted on pay.
"You know a government is in terrible trouble when they try to convince you that it is in your interests for you to have a wage cut," Mr Shorten said in Melbourne.
The government is next week expected to finalise its submission to the Fair Work Commission's penalty rates decision.
The commission has asked for comment on how the decision should be rolled out, including whether "take-home pay orders" should be issued.
The purpose of such an order is to compensate an employee for any reduction in their pay as a result of the making of a modern award, or the transitional arrangements in a modern award.
Since 2010 about 140 applications have been made for take-home pay orders, with five granted, 12 refused and the remainder either withdrawn, settled or adjourned indefinitely.
The last order to be granted was in November 2013.
Employment Minister Michaelia Cash has asked her department for advice on how take-home pay orders might work, promising a "factual" submission to the FWC.
Phasing in the penalty rate cuts over a period of years could minimise the hip-pocket pain, as the impact of reducing the penalty rate on the overall pay-packet is offset by the rise in wages from annual wage review decisions.
