Mr Mailler claimed Mr Joyce's inaction on wheat stocks reporting had cost growers dearly. 

It's an attack that is unfair, say Mr Joyce's office, who point to drought and global supply factors as contributing factors to the declining revenue for wheat growers.

Mr Mailler was the chairman of the national grower representative organisation, Grain Producers Australia when the Wheat Export Marketing Amendment Bill was passed in late 2012. 

One of the Act’s conditions was bulk handling companies would make available weekly wheat stocks information during harvest (and monthly thereafter) to describe wheat in store by grade and by port zone to producers. 

Mr Mailler said the value of the information was then conservatively and independently estimated to be worth three to five dollars per tonne of wheat to Australian growers, and would have helped level the playing field in the grain marketing system between producers and the bulk handling companies.

“Mr Joyce has held office for three wheat harvests, and Australian producers have produced approximately 75 million tonnes of wheat in that time,” Mr Mailler said.

“Mr Joyce has cost growers about four dollars per tonne of wheat produced in lost revenue by failing to enforce the conditions of Wheat Export Marketing Amendment Bill.  

“That equates to approximately 300 million dollars in lost revenue to the production sector on his watch. The accepted economic multiplier for Australian farm income is a factor of seven. As a result, Mr Joyce’s inaction has cost our economy approximately 2.1 billion, and most directly affected is the regional economy.”

A spokeswoman for Mr Joyce said it was incorrect to assert Mr Joyce’s actions had cost growers $4 per tonne.

“Wheat prices and export volumes in recent years have been affected by drought and global supply factors in particular,” she said.

“But don’t take my word for it.

"Fortunately, a recent report by a student from the University of Western Australia considered this simplistic claim and rejected it.”

The article referred to was called 'Deregulation of Australian wheat export market not responsible for high price volatility' and was published on the university’s website on Tuesday, May 24.

Mr Mailler said the $4 per tonne had nothing to do with global markets, droughts, the single desk or wheat marketing deregulation. 

“This is all about lack of transparency in the supply chain, in the same way the dairy industry has a lack of information to growers, and beef,” he said. “What we had was a guarantee in the Act for the provision of the basic level of stock information to help growers make better decisions, and Mr Joyce has not enacted it.”

Independent candidate for New England Tony Windsor said he agreed with Mr Mailler’s assessment.

“There’s an issue of stocks disclosure here that’s undoubtedly cost the industry an enormous amount of money over the ensuing years,” Mr Windsor said.

“A small marketer in Inverell, Tamworth, or a grain-grower at Gravesend are not going to be able to know what stocks are left in Australia or what quality is in various storages.

"So when they want to make planting, marketing or purchasing decisions, they’re almost blind in terms of the product that’s really out there.”