There have been reports of GM contamination of up to 0.5 per cent in some commercial canola varieties.

Pete MacSmith, from MacSmith Milling in New South Wales, says his customers are becoming concerned they are paying a premium for canola, which may not be GM-free.

"What our customers and what everyone's customers are looking for is certainty," Mr MacSmith said.

"Japan as we know already takes GM canola from countries such as Canada and I know it's hard to believe for canola growers given where the price is at the moment, but canola from the east coast of Australia at the moment is relatively expensive in world terms due to the much smaller crop.

"If our customers in Japan are going to pay a higher price they need some sort of certainty as to the status of that crop."