Four "fast fashion" brands were named in China's top 5 worst in terms of safety among imported garments, quality supervision officials said.

Forever 21, Zara, H&M and Mango were the most frequently found to fail quality and safety tests in recent trials, the General Administration of Quality Supervision, Inspection and Quarantine said in an online statement.

A total of 12,305 cases of imported apparel, worth 47.67 million U.S. dollars, were found to have failed quality tests in the first half of this year.

An overwhelming majority (over 97 percent) failed quality tests due to lack of clear instructions in Chinese.

Of those, 396 cases failed safety tests. The four "fast fashion" brands accounted for 107 cases, or 27 percent of the total, the Administration said.

Clothing can fail safety tests if they are found to be potentially hazardous to consumers or the environment.

For example, 1,442 imported children's garments failed quality tests after a significant portion failed to meet pH level standards - which could result in harm to children's skin.

China demands all imported apparel should be inspected by the country's quality watchdog before entering the Chinese market.