Consumers wondering whether A2 protein-only milk can make them "feel better" may have to wait until November 2017 for some insight, when a court battle between ASX-listed The a2 Milk Company and Japanese beverage giant Lion Group will be heard.

The legal stoush began in June, when a2 Milk disputed Lion's use of the term "A2 Protein" on labelling for Lion's PURA and Dairy Farmers products.

Milk products produced by a2 Milk come from dairy cows that produce only the A2 type of beta-casein protein. That is unlike regular cow's milks, such as that used in PURA and Dairy Farmers, which contain both A1 and A2.

The marketing and product proposition behind a2 Milk is based on a long-running claim that its A2 protein-only product reduces digestive discomfort, and causes consumers to "feel better."

In its statement of claim, a2 Milk accused Lion of engaging in misleading and deceptive conduct by making A2 protein claims that led consumers to think its products were "the same or similar".

But in a cross claim filed at the end of August, Lion scrutinised the science behind a2 Milk's health-related claims, and alleged false representations and misleading and deceptive conduct.

Among the false representations alleged by Lion, are that "milk containing a mixture of A1 and A2 beta casein is unnatural," and that "over 100 scientific studies" have established "that milk with no A1 beta casein affords health or digestive benefits."

In a directions hearing in the Federal Court on Friday, a2's barrister, Cameron Moore, SC, said what remained unclear was "the gambit of the scientific debate," and whether there was true opposition from Lion to the proposition that consumers experienced health-related benefits from A2 protein-only milk.

Justice Michael Wigney said he felt there was "some scope for scientific debate," noting that "it seems to me to be a mutually self-destructive piece of litigation, in some ways."

Lion's barrister, Neil Murray, SC, said the extent to which the case would be a scientific debate would be made clear by the evidence. Mr Murray disagreed with Justice Wigney's statement the case was "mutually self-destructive."

"We think these cases are not flip sides of the same coin, we see them fall out quite differently," Mr Murray said.

Australia and New Zealand chief executive for a2 Milk Peter Nathan told Fairfax Media his brand was confident, and believed Lion was "conning consumers".

"From the moment they changed their label [to say 'Naturally contains A2 Protein], the milk has never changed, it is the same product," Mr Nathan said.

"We are entirely confident about the veracity of our claims. If there is no benefit, why did they put the proposition on their product?"

Mr Nathan also said: "if our claims were misleading, then why didn't they challenge us when we first made them [in 2000]?"

In a statement, Lion said it believed a2 Milk had engaged in misleading and deceptive conduct by "claiming that a2 milk has benefits which cannot be substantiated, as well as that ordinary dairy milk can have adverse health consequences for consumers.

"Lion believes that all dairy milk is good for you. Lion is confident its claims and packaging are accurate and intends to vigorously defend a2's claims," Lion's statement said.

Lion has until December 14 to amend its cross-claim, when the next directions hearing takes place.

The matter has been set for hearing for two weeks from November 27 next year.

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