The central government has ordered a two-month law-enforcement campaign to halt the use and production of highly poisonous chemicals.

The campaign, to last from August to September, is in response to news reports that "a dozen or so" pesticide producers were still making highly poisonous pesticides such as methylamine and phosphamidon.

The five types of pesticides, banned earlier this year, are also highly polluting.

Other less polluting pesticides are accepted in international practice and will not pose a threat to farmers or consumers.

Wang Shoucong, deputy director of the Ministry of Agriculture (MOA) department of farming management, told China Daily the ministry is compiling a blacklist of law-breaking companies.

He said there are only three companies still authorized to produce the banned chemicals, which will not be used unless in emergency situations to control pests, and under strict government supervision.

Prior to the ban, the chemicals were produced by as many as 1,500 pesticide manufacturers, about half the industry.

However, the MOA official said, "improper use" of chemicals still existed in rural China, where some farmers spray pesticides on their crops shortly before they are harvested and sold.

It is difficult to monitor the use of pesticides on millions of household farms, he conceded.

As part of the government's food safety strategy, it will educate farmers how to properly use pesticides.

Official data shows that the overuse of pesticides has been rampant in China. The country sprays 1.45 million tons of pesticides annually, almost two times more than necessary.

Du, a seasoned expert in China's agricultural reform, said the overuse of pesticides, coupled with growing industrial pollution, have caused grave food safety concerns.