A report in the UK journal New Scientist states that this is the first time cow's milk has been engineered to improve its quality, rather than to contain profitable pharmaceuticals.

"The cows possess additional copies of genes for two proteins, beta and kappa casein. As a result, their milk contains between up to 20 per cent more beta-casein and twice the amount of kappa-casein as milk from ordinary cows," writes the journal .

According to the report, the modification should allow cheese-makers to produce more cheese from the same volume of milk. The manufacturing process should also be quicker, due to the faster clotting times associated with the higher protein levels.

"Basically, cheese is casein,"Goötz Laible , who led the work at the Ruakura Research Centre in Hamilton, is quoted as saying in the New Scientist report. "An increase in casein would certainly be of great value to the dairy industry, because farmers are paid on the basis of how much casein is produced in the milk."

Laible's team created a number of transgenic cell lines, each containing up to 39 additional copies of the casein genes. These were fused with cow eggs, and the cloned embryos produced were implanted in cows. Of 11 healthy offspring, nine produced increased amounts of casein.

But public cynicism and concerns about the safety of eating foods produced by genetically modified animals will be a clear barrier to growth in this potential market.

GM ingredients are used infrequently in food formulations by food manufacturers anxious for buoyant, not falling, sales. But Brussels recently pushed through tough new rules on the labelling of GM ingredients - that flag up such an ingredient on the food label - in a bid to make such foodstuffs more accessible to the market.

A recent report from UK consumer group Which? showed that six out of 10 people (61 per cent) polled said they were concerned about the use of GM material in food production - up from 56 per cent in 2002.

"Consumers clearly don't want GM food and are hardening their stance against it," said Malcolm Coles, editor of Which?.

The survey of almost 1,000 people also recorded a rise in the number who said they tried to avoid GM food and a fall in the percentage who backed the widespread growth of GM crops in the UK.

A report on the GM cow research in New Zealand was documented in Nature Biotechnology .