The Greens are pushing for superannuation payments on paid parental leave in exchange for supporting the government's tax changes aimed at wealthy retirees.
Greens spokesperson for women Larissa Waters confirmed the party would support the Labor legislation, which would increase tax on high super balances, if the government met its demands on paid parental leave.
Senator Waters said the bill was the perfect opportunity to add superannuation to Commonwealth-paid parental leave.
She said women, who tend to disproportionately bear caring responsibility, were "retiring into poverty".
"With a stroke of a pen, the government could fix that," she told ABC radio on Friday.
The Greens plan to use their balance of power in the Senate to nudge the government over the line, with the opposition already ruling out their support for the super tax concessions.
The federal government has signalled its interest in paying super to paid parental leave, but budget constraints have stopped Labor from taking action.
Senator Waters said the measure would be "relatively cheap" in the context of government expenditure, amounting to about $200 million a year.
She said the Greens were giving the government an opportunity to act.
"They've said it's a priority, well great, do it," Senator Waters said.
Treasurer Jim Chalmers said if the Greens supported tax reform to make concessions less generous for people with millions of dollars in super, they should vote for it.
"We've already extended paid parental leave as part of a multi-billion dollar agenda to support women's economic opportunity," Dr Chalmers said in a statement.
"We've already made it clear for some time that we intend to act on the super guarantee on paid parental leave when budget circumstances permit - that remains the case and we've said so publicly and repeatedly."
Under the plan, super balances above $3 million would be taxed at a higher rate.
Shadow treasurer Angus Taylor said the tax on wealthy super balances represented a broken election promise from the government.
"Our superannuation system is undermined when politicians break promises about it," he said in a statement.
"These are long-term decisions and long-term investments and Australians deserve certainty when planning for their retirements. Super is Australians' money, not the government's."
The opposition is yet to reach a formal position on whether it would support super payments on paid parental leave, with the party indicating it will examine the proposal.
Independent ACT senator David Pocock, whose vote the government needs to get the superannuation tax changes passed, said he supported the measure, along with the paid parental leave reform.
But he said he wanted to see the legislation for both proposals before formally backing it, warning against a deadlock on the issue.
"I want to make sure that conflating the two doesn't lead to neither being implemented," he said.
"The Greens and crossbench regularly use their balance of power positions in the Senate to push the major parties for better outcomes.
"However, I would hate to see this end up in the same place as the (housing fund), going nowhere with everyday Australians paying the price."