Scott Morrison has promised Western Australia's powerful resources industry he will make a fresh push to slash green tape and reform industrial agreements.
But unions are warning it will result in lower pay for thousands of construction workers.
The prime minister will revive efforts to extend the length of enterprise agreements for major projects if the coalition is re-elected on May 21.
Under the proposal, the maximum term for greenfields agreements would increase from four to six years for projects worth at least $500 million.
The government had unsuccessfully pushed for an eight-year limit during the last term in parliament.
"Far from putting jobs at risk, this is about seizing investment opportunities that create high-wage jobs in mining, construction, transport and manufacturing," Mr Morrison told the Chamber of Minerals and Energy in Perth on Tuesday.
The deals would include annual pay rises in line with the Fair Work Commission's annual wage review.
The Australian Council of Trade Unions said the minimum wage had increased 2.7 per cent on average since 2015, compared to 3.1 per cent for greenfields agreements over the same period.
ACTU secretary Sally McManus accused the prime minister of proposing to cut workers' wages "while protecting the profits of big business".
"These agreements can also lock in high levels of casualisation, labour hire and the use of temporary visa workers," she said in a statement.
"They remove any ability for workers to resolve and improve these issues, including negotiating pay increases that ensure workers are not suffering real wage cuts."
Asked whether Labor would support the change, frontbencher Tony Burke said the party's industrial relations policies were already locked in.
"Unlike the government, our industrial relations policies uniformly deliver secure jobs, better pay and a fairer system," he told reporters.
Industry groups including the Business Council of Australia welcomed the proposal, saying it would help to unlock investment in major projects.
Mr Morrison is also promising to reintroduce legislation enabling "single-touch" environmental approvals if the coalition wins another term.
A previous attempt to legislate the reform, which would hand primary decision-making power to the states on certain projects, failed to win support in parliament.
While federal Labor has been critical of the proposal, it is strongly supported by WA's Labor premier Mark McGowan.
The prime minister accused Opposition Leader Anthony Albanese of failing to support the resources industry.
"Mr Albanese and federal Labor sided with the Greens and against Premier McGowan, against Western Australia and against the resources industry," he said.
"His record of flip-flopping over the resources industry is well known - and he certainly wouldn't be able to stand firm when it comes to the Greens or the unions."
Mr Morrison earlier unveiled new resources investments which he said would create thousands of jobs and shore up supply chains.
The government will spend $140 million on developing two new hydrogen hubs in the Pilbara and Kwinana, near Perth.
A further $67 million will go towards developing two carbon capture and storage hubs as well as supporting the appraisal of a third potential storage site in WA.
And $50 million will be allocated to a partnership led by Curtin University aimed at commercialising research into critical mineral supply chains.
