Deputy Prime Minister Richard Marles is digging in after a confusing week of debate about income tax cuts.
Mr Marles said while the government was openly discussing the pressures on Australia's finances, it would not scrap the cuts due in 2024.
"What we've consistently said is that our position on tax has not changed," he told the ABC on Monday.
"I don't think we could have been clearer than that.
"We've been making the point that the budget is under pressure and it's certainly under pressure looking into the medium and long term."
The government has been accused of moving to break a central election promise after flying kites over the future of the stage three tax cuts.
But the Greens are worried the government will need to rein in spending on critical services to afford the cuts.
"The Greens will not back budget austerity measures to help Labor fund their stage three tax cuts for politicians and billionaires," Greens leader Adam Bandt said.
"Labor's flat tax nightmare is tearing down social democracy, ripping money from public services to pay for $9000 tax cuts for politicians and billionaires."
The government has been upfront about pressures on the budget and says it will target wasteful spending to help improve its bottom line.
Mr Marles, who is also defence minister, said the government was looking to streamline military spending.
"The focus of what we are trying to say today is that the waste that we've seen in defence over the last 10 years must come to a stop," he said.
Anthony Albanese has also doubled down on the tax cuts, saying his government was not planning any changes.
But the opposition is calling on the prime minister to expressly rule out any amendments.
"Our position hasn't changed - I've said that repeatedly," Mr Albanese told reporters.
Nationals leader David Littleproud urged the government to stick to its election promise and keep the stage three tax cuts.
"We just simply cannot trust Labor with tax cuts," he said.
"These aren't tax cuts for the big end of town - this is for middle-income earners making between $45,000 and $200,000."
© AAP 2022