The Australian Greens want Treasurer Joe Hockey to delay a decision on a foreign takeover of GrainCorp until a Senate committee has finalised its inquiry into the US bid.
Mr Hockey must make a decision by December 17 after taking advice from the Foreign Investment Review Board.
The $3.4 billion bid by Archer Daniels Midland is threatening to split the Abbott government along coalition lines.
The Nationals vigorously oppose the takeover of eastern Australia's largest bulk grain handler and exporter fearing ADM will put its own commercial interests ahead of farmers.
A Senate committee looking at the bid tabled an interim report from its inquiry on August 30, a week before the federal election.
It recommended the competition watchdog reopen its informal review of the takeover.
The Australian Competition and Consumer Commission has given the green light to the ADM bid.
The Senate committee also warned there could be a potential loss of tax revenue from ADM's tax minimisation strategies.
Greens senator Rachel Siewert, a member of the committee, says the inquiry needs to be completed before the treasurer makes his decision.
Growers were rightly worried that ADM could implement changes, such as closing storage sites, restricting access to GrainCorp grain network or increasing fees, she said.
"There is also unease about ADM's corporate culture and the risk that this may introduce into the Australian market."
Mr Hockey said new investment was needed to develop Australia's produce and that meant welcoming foreign capital.
"It is worth reminding ourselves that each year we need $40-$50 billion of net additional foreign investment just to fund our lifestyles," he said in a speech to the Centre of Independent Studies on Friday.
While foreign capital might be plentiful now, Australia would have to fight hard for that investment, particularly in the region, he said.
"So I do want to send the message that Australia is most definitely back open for business."