Construction employers have launched a push to scrap Saturday penalty rates until the end of the year to deal with the economic impact of the coronavirus.
Master Builders Australia, Housing Industry Association and Australian Industry Group have made a joint submission to the Fair Work Commission asking for temporary award changes.
Under the proposal, 38-hour ordinary working weeks could be performed between 6am and 7pm Monday to Friday and 6am and 2pm on Saturday.
Casual shifts could be as short as two hours, while workers and bosses could agree to time off instead of overtime.
The CFMEU argues the pandemic is being used to attack wages and conditions, accusing employer groups of opportunism.
The construction union is opposed to changing the award.
Chief executive Denita Wawn said many building contracts signed before the onset of coronavirus were based on high productivity.
"We have had to slow down because of social distancing," she told Sky News on Tuesday.
"We're simply asking that by agreement, that employer and employee can come to an arrangement in a temporary way until the end of the year."
She said a predicted 40 per cent decline in work could hit a third of workers in the sector, putting 450,000 jobs on the line.
The opposition's industrial relations spokesman Tony Burke said cutting penalty rates did not lead to job creation.
"We need people to be spending money," he told Sky.
"If you look across the whole economy I find it really hard to see what the builders have argued today, that it in fact adds up."
The Morrison government is set to announce a construction package this week, with cash grants for new home construction and major renovations under consideration.
Master Builders wants $40,000 grants for new homes and a multi-billion dollar fund for safety renovations.
Labor leader Anthony Albanese called for the government to stop ignoring support for social and affordable housing.
"Social housing is an investment that produces a return, of course, for government because it's an asset," he told reporters in NSW.
Greens leader Adam Bandt described the government's plans as a "mansion extension fund".
"Under the Liberals, it looks like some Australians may be gifted public money to add extra rooms to their empty mansions while others are battling frostbite on the streets," he said.
Australian Associated Press