Piece rate facing minimum wage challenge in Fair Work Commission

However, the National Farmers' Federation will fiercely oppose the move, which it says would effectively abolish a method that "rewards a fair day's work with a better than fair day's pay".

AWU has been campaigning against the piece rate, insisting the system had been manipulated to lead to widespread incidents of workers getting paid just a few dollars an hour.

"The farming lobby loves piece rates because their complexity is a great place for wage thieves to hide," AWU national secretary Daniel Walton said.

"Currently you don't even need to record how many hours someone is working. If we're serious about cracking down on wage theft and abuse then we have to put a floor under piece rates.

"The farm lobby loves to claim that workers on piecework arrangements make more than the minimum wage. If that's the case, what we're proposing should have no impact on them."

However, NFF chief executive Tony Mahar said AWU was "deliberately and incorrectly" conflating the very serious issue of worker underpayment with piecework rates.

"For PR purposes, the AWU likes to roll out lines about farm workers being paid $3 an hour - if this is accurate, it is clearly an instance of underpayment and completely unrelated to the operation of piece work rates," Mr Mahar said.

"Employers who deliberately rip off workers must be held to account.

"By contrast, piecework rates are a legal payment mechanism, that already have a built-in protection mechanism that guarantees workers earn 15 per cent more than the award wage."

Mr Mahar said the risk of putting in a minimum floor price on piece work rate was that growers would see productivity and the pool of suitable workers drop, at a time when the industry was already battling a labour shortage.

"Rather than offering a set, hourly rate, piecework rates allow workers to earn at a rate that directly corresponds to how much they pick or pack in a given workday," he said.

"A worker on an hourly rate might earn less than $25 per hour over 7 hours and pick 5-6 bins of apples, over the same period, a worker on piece rates might earn $45 per bin, effectively doubling their earnings."

Mr Walton said if AWU won the case, it would help attract Aussie workers back into the sector.

"The so-called labour shortage has been created by greedy employers destroying working conditions," Mr Walton said.

"Introducing the minimum wage would give locals confidence they can work in this sector without being ripped off."