"It stands to reason that we are more likely to be exporting food to South-East Asia than exporting cars," said Senator Barnaby Joyce.

"[But] I don't have a choice; nor do I have any sign of a government that is willing to make the small steps towards a better future in agriculture. I do believe Australia should have a manufacturing industry."

The Australian Financial Review reports Senator Joyce said the benefits of investment in agriculture were obvious.

"If people from overseas can see the future in Australian agriculture and they're gaining a substantial foothold in the prime sections of Australian agriculture, then there should be a flashing light going off for the rest of Australia."

General Motors and Toyota said on Tuesday they may ask for additional money on top of the estimated $1 billion they have received in the past decade to revamp engine plants and explore new local models.

National Party Leader Warren Truss said the Labor government had halved the budget of the Department of Agriculture from $3.8 billion to $1.7 billion since 2007.

He said the car industry would get an immediate boost under a Coalition government with the abolition of the carbon tax.

The Coalition remained committed to its $1 billion for the Automotive Transformation Scheme, Mr Truss said.

"Asia will increasingly look outwards for others to fill the food void and we are uniquely positioned on their doorstep," he said.

"But we, as a nation, need to be geared for growth if our farmers are to achieve their potential. That means investing in agriculture and regional infrastructure."

Labor backbencher Kelvin Thomson admitted the automotive manufacturing industry will not survive without government funding.