Comments by Holden at an inquiry have added fuel to the debate over the car maker’s future in Australia.

The federal government has demanded Holden immediately reveal if it will keep making cars in Australia, after again playing down the prospect of a hand out for the US-owned group.

Holden Australia boss Mike Devereux on Tuesday fronted a Productivity Commission inquiry and said the company hadn’t yet made a decision on the future of its South Australian and Victorian plants.

But he also signalled the company – which has been making cars in Australia for 65 years – was looking for long term support and could only keep going under a public-private partnership.

Acting Prime Minister Warren Truss urgently wrote to Mr Devereux seeking a clear explanation of the company’s intentions for jobs and operations under its US parent General Motors.

“An immediate clarification of GM Holden’s future plans is needed to end the uncertainty for Holden’s workforce, its suppliers and the people of Australia,” the letter said.

Treasurer Joe Hockey went further, bluntly challenging Holden to end the speculation.

“Either you’re here or you’re not,” Mr Hockey said in parliament.

The government’s mid-year economic review is due next week and is expected to show a budget deficit for this financial year of $40 billion or more.

Despite the fiscal constraints, Mr Hockey said there was no shortage of government funds going to the car industry.

“A hell of a lot of other businesses and foreign owned businesses … would love to be able to remit taxpayer money from Australian taxpayers to head office in Detroit, or London or Tokyo or anywhere else,” he said.

The Holden issue is dominating news as a second Newspoll on Tuesday showed the coalition government lagging Labor 48-52 per cent after preferences.

Holden told the inquiry the $1.8 billion it received from government programs from 2001 to 2012 had delivered a $32.7 billion spin-off in economic activity, including money paid to Australian automotive suppliers and tax revenue.

The federal opposition is pursuing the government over the $500 million it plans to cut from industry assistance, demanding the decision be reversed.

The opposition also called on Industry Minister Ian Macfarlane to release a new car industry plan before the Productivity Commission inquiry reports in late March.

“We have a process and we are going to stick to it,” the minister told parliament.

Mr Macfarlane said Labor had damaged the car industry through its introduction of the carbon tax.

“The coalition is committed to the car industry,” he said.

Labor frontbencher Doug Cameron, a former manufacturing union official, said the government didn’t care about the industry’s future.

“Unless we have a manufacturing base in this country, we will end up being a quarry, a farm and a tourist destination and that is not good enough,” he said.

Mitsubishi closed its auto operations in 2008 and Ford will end production in 2016.

Holden has suggested public funding of up to $150 million a year would secure its future.

South Australian Premier Jay Weatherill, who will meet with Prime Minister Tony Abbott in Canberra on Thursday, said the federal government could be in no doubt about what was needed to save Holden, while Victorian Manufacturing Minister David Hodgett will push for further federal funding.