Dozens of children's wear factories in east China's Zhejiang Province, have received serious warnings after 40 percent of their products were found to have quality problems, according to local quality supervision authorities.

In the latest inspection, only 44 out of 72 batches of children's wear products inspected in Wuxing District, Huzhou city, which produces a quarter of the country's children's garments, met standards and their "quality index" was the lowest since 2003, according to the Zhejiang provincial quality and technical supervision administration.

The inspection is only part of a four-month nationwide campaign to improve product quality and food safety launched in late August, after a series of quality problems in China-made products, ranging from toys to pet food, were exposed abroad.

Described by Vice-Premier Wu Yi as a "special battle" to ensure public health and interest and maintain a good image of Chinese products, the campaign has targeted farm produce, processed food, catering, drugs, pork, and imported and exported products.

The garments in Wuxing District of Huzhou had problems with the dyes, fibre content and stitching, said the local product safety administration. All the problematic garments were produced by non-exporting companies.

The administration gave a "yellow warning" to the Wuxing district, demanding the local government and factories immediately improve quality.

The samples of the unqualified products were confiscated and the garment factories were ordered to make substantial quality improvements within one year, said Feng Weijun, an official with the administration.