SHOPS in the UK are rationing sales of baby milk after Chinese visitors and bulk buyers cleared shelves to send it to China, where many parents fear local versions are not safe.

The British Retail Consortium said many stores had imposed a two-box limit on each customer to deter the "unofficial exports" to China.

Demand for foreign milk powder has been high in China since at least six infants died and 300,000 fell ill in 2008 after they drank milk laced with the industrial chemical melamine.

The scandal has sapped consumer confidence in Chinese-made food and led to shortages of powdered milk in Hong Kong and Australia as people bought boxes to export to China's mainland.

The rise of the richer Chinese working mother has greatly increased sales of baby milk. Fast-growing markets like China support a global baby food market worth an estimated US$30 billion a year.

"The major retailers of baby milk - supermarkets, chemists - are restricting sales," said BRC spokesman Richard Dodd. "They have done this in response to some customers buying unusually large amounts. The irregular buying patterns are thought to be a result of unofficial exporting to China."

The buyers include Chinese tourists and students who take a few cartons home with them or post them to relatives. There are also organized groups who buy large amounts of powder to export to China, one businessman involved in the trade told Sky News.

"There are three types of people like us. The first you get (are) students or visitors who get asked to send one or two tins back to family or friends. Then you get small and medium businesses like me," the man, based in northern England, said.

"The third group of people are the biggest sellers. They buy directly from health distributors - the kind of people who supply supermarkets."

Shoppers in London said they had noticed sporadic shortages and had to visit different chains to find a preferred brand.

"On Sunday, we couldn't get any in Asda or Tesco and we had to go to Sainsbury's," said Lyn Patterson, walking with her grandson Jacob in Oxford Street, one of the capital's busiest shopping areas. "They're sold out all the time. But we've never run out - we always have a carton on standby."