The government's election commitment to fund 30,000 social and affordable homes over the next five years is at risk of defeat, as the Greens continue threats to vote against it unless the government significantly steps up funding.
If the bill cannot win enough support to pass the Senate, it would be the first major defeat for the government, which made the housing fund a key pillar of the party's federal election campaign.
Despite being in negotiation for weeks, the Greens and the federal government have made little progress towards an agreement, though spokespeople for both parties maintain that discussions have been "constructive".
The bill to establish the $10 billion future fund is due to be voted on this week, but Greens housing spokesperson Max Chandler-Mather said the government's policy may not even achieve its own aims.
"It doesn't even guarantee that we would spend $500 million a year," Mr Chandler-Mather said.
"The plan as it stands is getting $10 billion and gambling it on the stock market via the future fund ... the problem is last year the future fund lost 1.2 per cent, so they would have lost 120 million dollars.
"Our point is for the millions of people in this country who need an affordable home, for the hundreds of thousands on the wait list for social housing; their lives shouldn't be dependent on whether or not a gamble on the stock market goes well - imagine doing that for schools or hospitals?"
The Greens have called for at least $5 billion a year to be injected into housing and say that is a fair amount, noting the National Housing Finance Investment Corporation's recommendation for at least $15 billion in social and affordable housing investment each year.
The party also wants more assistance for renters, as Mr Chandler-Mather said recent rent increases fuelled by inflation had left them "badly screwed over".
But the government has resisted offering a guaranteed minimum spend, even if the fund does not make returns.
On Friday, Housing Minister Julie Collins said the fund was already the biggest single investment in housing in a decade and that it worked in tandem with other government policies, including an agreement with the states and territories to build one million new homes over five years, accompanied by an additional $350 million over that time.
"We continue to have good discussions with the crossbench, and I'll continue to have those discussions," Ms Collins said on Friday.
Prime Minister Anthony Albanese said the government would be "happy" to pursue the issue at the next election if the fund was rejected by the Greens.
"If people think that it's a great idea to say that they support more investment in social housing, but not back a $10 billion fund that will build more social and affordable housing, then good luck having that argument, and I'm quite happy to have that argument between now and the next election," Mr Albanese said.
"Because some of the rhetoric about the Housing Australia Future Fund seems to think that this is in place of everything else, including the Commonwealth-state housing agreements that happen between the Commonwealth and state governments, that it's in place of the other things that we have announced as well in the housing sector.
"It's not. It's additional."
Mr Chandler-Mather told the ABC the government had "nothing to lose" in increasing its ambitions.
"How rare is it that you have everyone from conservative institutions like Master Builders all the way to the CFMEU, the crossbench and the Greens, everyone out there, housing experts, all saying it is time to spend actual money on housing," he said.
"Why would we support a plan that makes the housing crisis worse? The reality is right now, that's what their plan does."
Mr Chandler-Mather said the Greens would begin a doorknocking campaign on housing next month if the bill wasn't settled this week.
Senate crossbencher Jacqui Lambie said she and colleague Tammy Tyrrell were also yet to decide whether to support the housing fund but were equally concerned over how the fund was set up.
"This is going to come down to, once again, the Greens and whether or not they support it," Senator Lambie said.
"What we do know is whilst we're arguing over this, we're not getting any houses built. Get this done, and we can come after more money.
"For the Greens to say a flat no would be pretty disappointing ... it might not be great, it might not be the best thing, but right now we need a starting point, let's get moving."
Independent senator David Pocock has also withheld support over concerns that as the bill stands, the government would be building fewer social and affordable homes than the amount lost from the wind-down of the National Rental Affordability Scheme.
