Dissident dairy company A2 Corp today launched sales of its milk in New Zealand through Progressive Enterprises supermarkets in Auckland and Christchurch.

Tomorrow it plans to start selling in Dunedin, marketing the milk as a "risk free alternative" to standard milk produced by dairy giant Fonterra, which contains a mix of A1 and A2 beta casein proteins.

A2 Corp says its milk contains only A2 beta casein and has conducted a legal "knocking" campaign, claiming that health risks are associated with A1 milk.

A2 chief executive Corran McLachlan has claimed the beta casein A1 found in most cows' milk sold in New Zealand has been linked with the development of coronary heart disease, childhood diabetes and also implicated with autism and schizophrenia.

Food manufacturers are legally barred from making therapeutic claims for their foods -- such as being capable of curing illness -- unless they substantiate the claims with scientific testing and register the food as a medicine. But there are no regulations to stop them from disparaging rival products.

Between 20 per cent and 45 per cent of dairy cows on both sides of the Tasman already produce A2 milk, with the remainder producing either pure A1 milk or a mix of A1 and A2, but usually the various milks get mixed when combined at bottling plants.

A2 Corp plans to make its money out of providing tests for farmers to genetically identify their cows producing A1 and A2 proteins, so that herds can be licensed to produce A2 milk.

Today's launch follows a "pilot launch" in Australia, which Dr McLachlan said resulted in demand far outstripping supply.

New South Wales dairy company Fairbrae Milk has been marketing Jersey Gold A2 Milk, but telling its customers that "for legal reasons, we are unable to specifically state its possible benefits".

Instead, the company referred customers on its website to the offshore website of New Zealand's A2 Corporation.

The A2 website said: "Beta casein A1 may be a primary risk factor for heart disease in adult men, and also be involved in the progression of insulin-dependent diabetes in children."

Australian food manufacturers are legally barred from making therapeutic claims for their foods.

Fonterra has previously complained A2 Corp's marketing is irresponsible and could undermine public confidence in milk.

The A2 milk will be sold in New Zealand through Foodtown, Woolworths and Countdown supermarkets and was launched at Foodtown Greenlane.

A two litre bottle is selling from $3.49, compared with $3.13 for Dairy Foods' Anchor brand, produced by Fonterra, $2.92 for the Signature brand and $2.80 for Basics brand.

Dr McLachlan said in a statement the New Zealand launch was an important day for A2 Corporation "as we are now able to offer consumers A2 milk which is free of the health risks associated with beta casein A1".

The standard milk on the New Zealand market at present contained beta casein A1 which had been strongly linked to heart disease and Type 1 (childhood) diabetes "amongst other illnesses", he said.

"International research carried out independently of A2 Corp along with A2 Corp's own sponsored studies have shown a close link to A1 milk protein fragments and arterial damage in both laboratory and animal research programmes."

Dr McLachlan has argued ancestors of wild cattle produced milk with beta casein A2, but that a genetic tendency to produce beta casein A1 was bred into modern farmed cattle because it was also associated with higher levels of milk production.

The first A2 milk on the New Zealand market has been supplied by a Waikato-based milk processor Ridge Group for the North Island.

In the South Island, milk is being supplied by International Dairy Ventures, where one of the directors is Brent Thornton, who has complained that Fonterra had been using its industry muscle to prevent farmers from supplying A2 milk to independent processors.

Dr McLachlan said it had been a struggle to get A2 milk on to the market as Fonterra had been using clauses in the Dairy Industry Restructuring Act 2001 to prevent or delay its farmers from supplying A2 milk.

The Act allows Fonterra to prevent its farmers from supplying any speciality milk protected by any patent processors other than Fonterra.

Farmers supplying milk to A2 Corporation licensees had either terminated their Fonterra supply contract or had divided up their herds to establish a separate A2 herd.