Federated Farmers has complained to the Commerce Commission, that there is unfair trading in the industry.
It has requested an investigation into what it calls breaches of the Commerce Act, involving differences in pricing and restrictive trading.
Grains Council chairman Ian Morten says growers want to know why New Zealand wheat growers are being about $100 per tonne less by Viterra, a Canadian-based company, than what is paid for wheat imported from Australia.
He says New Zealand wheat should be at a premium as it is a lot easier to handle and is quicker to get.
Mr Morten says there is not a lot of profit in grain growing at the moment and some growers are being forced to look at other forms of farming, like dairying.
The Commerce Commission has confirmed it has received the complaint and says it is currently being assessed.