Greens leader Adam Bandt says he would be astounded if Labor refused to "respect" the choice of voters by shunning his party in a hung parliament.
The minor party has unveiled a plan to protect existing mum-and-dad investors by grandfathering negative gearing and capital gains tax for people with one investment property.
Negative gearing allows investors to claim deductions on losses and the capital gains tax discount halves the tax paid by Australians who sell assets owned for 12 months or more.
In an address to the National Press Club on Wednesday, the Greens leader said the proposal would be used as a bargaining chip should Labor want his party's support to form government after the May 3 election.
Prime Minister Anthony Albanese has repeatedly insisted there will be "no deals" with the Greens in the event of a hung parliament.
But Mr Bandt said the penny was dropping for the major parties, with polls indicating both will struggle to reach the necessary 76 seats to form a majority government.
"I would be astounded if the prime minister, or anyone else, refused to respect the parliament that the Australian people choose," he said.
"If he can convince 51 per cent of the population to vote for him then OK, but that's not what happened. That's not what he did last time.
"With more people saying they want more voices at the table as part of a strong crossbench, he's going to have to learn to play well with others."
Labor election campaign spokesman Jason Clare ruled out potential tax changes.
"No, flat-out no," he told Sky News on Wednesday.
"What we want to do is build more homes."
Former Labor leader Bill Shorten went to the 2019 election promising to curb negative gearing, before losing.
The Greens have said they would not help the coalition to form government.
Mr Bandt said Australia needed to renegotiate the ANZUS Treaty, a security agreement signed after the end of World War II.
"We've got Peter Dutton, who wants to bring Trump-style politics to Australia, and Anthony Albanese ... going out and inviting Trump to come to Australia," he said.
"As if sucking up to these bullies is going to change the way they do things."
The Greens, who have four lower house MPs, are also pushing for a freeze on rents and adding dental treatment for adults to Medicare.
