Nationals leader Warren Truss has "serious reservations" about GrainCorp being sold to an American company but accepts it's a decision for the treasurer after the election.
Grain giant Archer Daniels Midland (ADM) has launched a $3.4 billion proposed takeover of GrainCorp, one of Australia's largest listed agribusinesses.
The takeover still needs the approval of Australia's Foreign Investment Review Board, but the Australian Competition and Consumer Commission has approved the bid.
GrainCorp shareholders have been given until November 16 to decide whether to sell.
Mr Truss said he doubted whether the sale was in the national interest.
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The deal would mean ADM, Cargill and Glencore would control almost 60 per cent of Australia's wheat shipments and put most of the nation's grain export infrastructure in foreign hands.
"That leads to where we will lose control over our own destiny and our capacity to expand our grain industry - those decisions would be made in board rooms in the US and other parts of the world," Mr Truss said.
He said the final decision would be in the hands of the next treasurer.
"I have certainly indicated to both sides of politics I have reservations about this matter but respect the fact the decision is ultimately the treasurer's," he said.
"I am confident a coalition treasurer will seriously and meaningfully address concerns."
