BEIJING - Experts are encouraging the government to raise the country's food quality standards and change the practices that cause food products for export to be safer than those for sale in the domestic market.

Official statistics show that food products for sale in overseas markets have passed quality tests 99.8 percent of the time in past years, while those sold in the domestic market have passed only 90 percent of the time, Xinhua News Agency reported without identifying its source.

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Some manufacturers seem to have an unwritten rule leading them to sell their highest quality products abroad and their second best at home, said Dong Jinshi, executive vice-president of the International Food Packaging Association, a Hong Kong-based non-government organization.

The existence of a double standard was revealed in the milk scandal that broke out in 2008. Many Chinese dairy companies were then found to be using the poisonous substance melamine to increase the apparent protein content of milk, sickening, as a result, 300,000 children and killing six others.

Mengniu, a milk product giant in China, reported in a statement to the Hong Kong Stock Exchange on Sept 23, 2008, that its liquid milk products are safe. It said Hong Kong food inspectors had tested 41 samples from its products and found all of them to be free of contamination.

In the same statement, the company admitted that all of the contaminated products it had manufactured had been sold in the mainland and said the tainted products had been recalled.

FSPG High-tech Co, a plastic manufacturer in Foshan city, South China's Guangdong province, used toxic materials to make fast food containers for the domestic market, China Central Television reported in January.

According to reports, Chen Yuewen, in the company's export department, admitted that safer materials had been used in making plastic boxes for overseas customers.

China's current quality and safety requirements for food lag behind those of many developed countries, which is a large reason for the low standards maintained for products sold in the domestic market, Dong said.

"Our quality threshold is relatively low, which has failed to force some food manufacturers that sell poor-quality or fake products to clean up their operations," Dong told China Daily on Wednesday.

Dong's words were echoed by Qiu Baochang, director of the Beijing Lawyers Association's consumer rights protection committee.

"It's a shame that some of our standards cannot keep pace with the changing situation in the market, and have even remained unchanged for over 20 or 30 years," Qiu was quoted by Xinhua as saying.

On the other hand, some foreign companies that make money from Chinese customers have also taken advantage of China's regulatory loopholes, Dong added.

Studies conducted by scientists from the Karolinska Institute in Sweden suggested that lead, arsenic and other toxic metals have been found in infant foods produced by Nestle and other multinational food companies, according to previous media reports.

But the Chinese Center for Disease Control and Prevention said in a statement over the weekend that the amount of toxic elements found in those brand products did not exceed its official safety limits.

Given the growing number of food scandals, stricter rules on food production should be adopted, Dong said.

Wang Dingmian, former vice-chairman of the Guangdong Provincial Dairy Association, said he believes that Chinese customers' preferences for low-price products have prompted food producers to use any means to cut their costs, even by sacrificing the products' quality.

"For many Chinese manufacturers, a product can be sold at a much higher price overseas," Wang said, adding that fierce competition in the domestic market has given them little room to make a profit.

Wang said Chinese customers, though the victims of the dual standards, should also change their consumption habits.