The scandal of contaminated milk formula that has killed four children spread to liquid milk and yoghurt ices yesterday, provoking an international backlash against Chinese dairy products.

Starbucks sold only black coffee in two thirds of its cafés in China, while the World Health Organisation called on Beijing to explain why it took months to report that companies had sold milk powder tainted with industrial chemicals as baby food.

The scandal spread beyond mainland China with Singapore banning the import of all milk and dairy products and Hong Kong pledging to pass a law banning the chemical in question, melamine - used to make plastic cups and saucers and in glues - from food. It has been added to the contaminated milk to increase its protein content. Chinese officials said that the contamination, probably caused by unscrupulous workers at milk collecting centres, could have been going on for years. Manufacturers have now recalled tainted milk powder exported to Bangladesh, Yemen, Gabon, Burundi and Myanmar.

Official figures say that 1,300 babies are still in hospital, 158 with acute kidney failure. The powder can cause kidney stones and other complications.

A count from the Government early in the week said that 6,244 children had fallen sick. Since then no new numbers have been issued, even though officials said that they expected the number of sick babies to rise. Thousands of parents have poured into hospitals across China to seek treatment for newborns who they fear have been fed adulterated milk powder produced by the once-prestigious Sanlu Group.

The crisis broadened when the Government's leading quality watchdog accused three top producers, spreading fear over dairy products. Almost one tenth of liquid milk samples from the giant Mengniu Dairy and the Inner Mongolia Yili Industrial Group have been found to contain melamine - although not in the enormous concentrations in baby milk powder. Sales of domestic milk products have slumped, with consumers turning to imports or alternatives such as rice water, in the latest shock to the “Made in China” marque.

“My grandson is fine because we buy him foreign brand powder, but I think it is terrifying that something like this could happen,” said Xu Li, who was shopping in a Beijing supermarket.

The World Health Organisation has demanded that Beijing find out why it took months to report the contamination. Hans Troedsson, the WHO China representative, said that the Government had to find out if the delay was deliberate or due to ignorance.

Robert Madelin, director-general for health and consumer protection at the European Commission, said that it expected a full accounting and the punishment of any cover-ups.“We are trying to establish the facts,” he said. “Our priority is to ensure the integrity of the European supply chain.”

Reports of the problem surfaced last week only after Helen Clark, the New Zealand Prime Minister, said that the food giant Fonterra had been trying for weeks to persuade its Chinese partner, Sanlu Group, to recall the milk powder.

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