Retailers are keen to be seen to have enough stock as Food and Health Secretary Dr Ko Wing-man has promised to scrap the two-tin limit imposed on outbound travellers if it is found there is enough for the local market. Consultants employed by the government will pay visits to pharmacies to check stocks during and after the holiday.

Chiu Chow Dispensary in Mong Kok, which joined the coupon scheme, set aside about 30 boxes of formula labelled "stock reserved for test, don't move". Staff at its other Mong Kok branch were telling customers they suspected were parallel traders that there was no stock. Pharmacies outside the scheme faced a severe shortage.

Some in Causeway Bay said they had kept running out all of last month. "We kept asking the manufacturer for more supplies, but it has been proved useless," a staff member of Fu Da Pharmacy, giving his name as Ngan, said.

"We do not sell to parallel traders or non-local mothers, but our stocks can rarely meet the locals' demand. And the problem only happens to Mead Johnson, it is a big headache," Ngan said.

Suppliers' hotlines are also being assessed by the government but only one was working on the public holiday yesterday.

Mead Johnson hotline staff told the yesterday that the company's products were not available for local mothers at designated pick-up points in areas like Tai Po, Fanling and Sheung Shui.

"You could try Sha Tin, where one store has two cans remaining," the service officer said.

"Parents can make reservations by leaving their registered name, membership number and telephone number with us."

Dicky Yu, 30, from Tseung Kwan O, who has a one-year-old son, said the government should not lift the two-can export limit, imposed earlier this year to combat severe shortages caused by parallel-goods traders buying formula to sell in Shenzhen.

"Before the rule was imposed, I wasn't able to buy formula anywhere," she said. "Stocks were much more adequate after the rule came in and pharmacies lowered their prices too."

Alan Leong Kah-kit, chairman of the Legislative Council's food safety and environmental hygiene panel, said it was unacceptable that so many shops were so short of stock when they knew in advance about the tests.

"I don't see how at this juncture the government can consider lifting the ban," he said.

Hong Kong General Chamber of Pharmacy chairman Lau Oi-kwok confirmed they were told of the coupon scheme in June, but refused to say whether the chamber helped design it.

A Mead Johnson spokeswoman said it was monitoring the market and would be working closely with retailers to ensure stable supply for local demand. Parents could order products via the company hotline or website.