Scientists in China have created genetically modified cows that produce "human" milk.
They successfully introduced human genes into 200 dairy cows to produce milk with the same properties as human breast milk.
Human milk contains high quantities of nutrients that can help to boost the immune system of babies and reduce the risk of infections.
The scientists behind the research believe that milk from herds of genetically modified cows can provide an alternative to human breast milk and formula milk for babies, which is often criticised as being an inferior substitute.
They said genetically modified dairy products from herds of similar cows could be sold in supermarkets and the research has the backing of a major biotechnology company.
British scientists said it had the potential to be of huge benefit, but the work is likely to inflame opposition to GM foods.
Critics of the technology and animal welfare groups reacted angrily to the research, questioning the safety of milk from genetically modified animals and its effect on the cattle's health.
Prof Ning Li, the scientist who led the research and director of the State Key Laboratories for AgroBiotechnology at the China Agricultural University, insisted that the GM milk would be as safe to drink as milk from ordinary dairy cows.
"The milk tastes stronger than normal milk," Prof Li said.
"Within 10 years, people will be able to pick up these products at the supermarket."
The rules on research into genetically modified food are more relaxed in China than those in place in Europe and its scientists are leading the way in the field.
The researchers used cloning technology to introduce human genes into the DNA of dairy cows before the genetically modified embryos were implanted into surrogate cows.
Writing in the Public Library of Science One, a scientific peer-reviewed journal, the researchers said they were able to create cows that produced milk containing a human protein called lysozyme.
It is an antimicrobial protein found in large quantities in human breast milk and helps to protect infants from bacterial infections during their early days of life.
They have also created cows that produce another protein from human milk called lactoferrin, which helps to boost the number of immune cells in babies.
The scientists disclosed at an exhibition at the China Agricultural University that they had boosted milk fat content by about 20 per cent and had also changed the levels of milk solids, making it closer to the composition of human milk as well as having the same immune-boosting properties.
Prof Li and his colleagues, who have been working with the GenProtein Biotechnology Company in Beijing, said their work had shown it was possible to "humanise" cows milk.
They said they had produced a herd of about 200 cows that were able to produce human-like milk.
The "transgenic" animals were physically identical to ordinary cows.
"Our study describes transgenic cattle whose milk offers similar nutritional benefits as human milk," said Prof Li.
"The modified bovine milk is a possible substitute for human milk," he said.