European fashion giants H&M and Zara have defended their quality control measures in the wake of a damning report by China's inspection and quarantine authorities this week. Inditex, Zara's parent company, told the South China Morning Post it "strives to ensure that products meet the most stringent health, safety and quality standards, including those set by the authorities in China". On Wednesday, the mainland's General Administration of Quality Supervision, Inspection and Quarantine said that products from Zara, H&M, Mango, and Forever 21 accounted for more than 25 per cent of clothing quality issues found in the first half of 2014. The quality control watchdog did not specify the exact problems, but China Radio International later reported that most cases involved excessive pH levels in the clothes, which can cause damage to people's skin. This is not the first time Zara has run afoul of authorities on the mainland. Since the Spanish fashion retailer's 2006 China debut, it has been singled out by the quality control watchdog more than 15 times, according to Chinese newspaper Time Weekly . "One of the reasons [these brands] are so popular is that they can quickly respond to customer preferences to bring new products to stores," said Mariana Kou, a retail analyst at CLSA. Speed comes at a price however, and quality control is often the first to suffer. "They will have to fix this as it will hurt the brand," she said. "Customers are becoming more conscious of this issue and they will have to do some damage control." A total of 12,305 cases of substandard clothing were discovered by the watchdog between January and June, with a value of more than US$37 million. More than 97 per cent of those cases involved missing or mistranslated Chinese labels. Both Zara and H&M emphasised the stringent testing they have in place to ensure that products meet quality requirements. H&M Hong Kong spokeswoman Cher Chui said the company carries out around 500,000 quality control tests a year, while Zara said that it conducted one million tests on products last year. Chui said the main problem highlighted by the watchdog was a lack of Chinese labels.