Treasurer Joe Hockey is facing a major test of his resolve as he decides whether to allow the foreign takeover of GrainCorp, Labor says.
Mr Hockey must make a decision on the proposed takeover of the bulk grain handler and exporter by December 17 after taking advice from the Foreign Investment Review Board.
But the $3.4 billion bid by US grain giant Archer Daniels Midland is threatening to split the government along Coalition lines.
The Nationals vigorously oppose the takeover, fearing ADM will put its own commercial interests ahead of farmers.
Opposition Leader Bill Shorten said: "This is a real test for the Coalition. Will Joe Hockey be consistent to his city-based, Liberal free market views, or will he listen to his National and country Liberal colleagues?"
Mr Shorten believes Mr Hockey will ultimately approve the takeover. "I think they'll try to put some conditions around it to make it look like they haven't simply acquiesced to that free market philosophy."