Chinese scientists have produced a herd of genetically modified cows that make milk that could substitute for human breast milk - a possible alternative to formula in a nation rocked by tainted milk powder scandals.

Researchers at the State Key Laboratory of Agrobiotechnology of the China Agricultural University introduced human genetic coding into the DNA of Holstein dairy cow embryos, then transferred the embryos into cow surrogates.

In 2003, after years of testing on mice, scientists managed to create the first cow that could produce milk with the same nutritional properties as human breast milk, but with a taste even stronger and sweeter.

"The genetically modified cow milk is 80 per cent the same as human breast milk," said Li Ning, a professor and the project's director as well as lead researcher.

"Our modified cow milk contains several major properties of human milk, in particular proteins and antibodies which we believe are good for our health and able to improve our immune system."

Over 300 cloned cattle now live on an experimental farm in suburban Beijing, with new calves delivered every week.

Li's team, which is supported by a major Chinese biotechnology company, aims to have an affordable form of the milk on the market within three years.

Behind their efforts is a series of poisonings and toxin scandals that have shaken consumer trust in China's dairy sector and its products.

In 2008, at least six children died and nearly 300,000 fell ill from drinking powdered milk laced with melamine, an industrial chemical added to low quality or diluted milk to fool inspectors checking for protein levels.

Before the milk can be marketed, for other people as well as babies, stricter safety tests are needed, Li said.

"In fact, we still need to conduct clinical trials on human beings with volunteers and finally prove that the cow milk is good and safe for the elderly, infants and the ill, especially those suffering from chronic diseases," Lid added.

"Only after these steps are completed can the government examine it and approve a certificate for its commercial use."

Despite the potential, the team's breakthrough has drawn criticism from opponents of genetically modified food who question the safety of the milk for humans. Others worry about the impact on the cows' health.

Greenpeace notes that China has been investing considerably in genetically modified food research in recent years, despite the lack of a credible, independent system of supervision and inspection.

It also insists that genetically modified products should not be allowed to enter the human food chain.

Chinese parents had a mixed response, with some wary but willing to give the milk a try while others were far more cautious.

"I won't try it. Even if it's similar to human breast milk, it's still genetically modified," said a woman who gave her family name as Lu, the mother of a 14-month-old girl.