South Australian Premier Jay Weatherill says Holden could shut down the Elizabeth production plant in northern Adelaide unless state and federal funding is secure.
The car maker this week announced a $153 million loss.
Holden recently announced a plan to cut hundreds more jobs at the Adelaide plant due to lower car sales, as well as more job cuts in Victoria.
The Coalition has said it will cut $500 million of car industry funding if it wins the federal election.
Mr Weatherill says that makes uncertain the future for the Elizabeth plant.
"The South Australian Government is committed to the current investment. What we need is a willing Commonwealth partner," he said.
"The current Federal Government is committed. What we need to know is whether Tony Abbott's Liberals will be committed to a future for Holden should they form a government after September.
"If they get their way, there will be no deal with Holdens about their future and therefore Holdens will close."
He has been in talks with Holden about government support, in light of the latest planned job cuts.
The Australian Manufacturing Workers Union says Holden employees have been on an "emotional rollercoaster".
Union secretary John Camillo says up to 450 workers at the Adelaide plant are considering the 400 redundancies Holden is ready to offer.
He says the union will discuss the voluntary separation packages at a meeting with Holden next week.
"We want Holden to let us know how many production workers they're looking at, how many people from trade, how many people from the white collar area and so on, but also it gives us a chance to know how many people are taking a VSP, because if Holdens don't get the 400 they require then seriously the unions and the company need to sit down and work out how we go forward," he said.
Mr Camillo says morale at the Elizabeth plant is low and worries high.
"People are very worried in regards to whether there's forced redundancies, whether they're going to be tapped on the shoulder and they'd be asked to leave the premises and so on," he said.
"People are very worried in regards to the future of the automotive industry in Australia and so on. At the moment they're going through this emotional rollercoaster."