Shanghai-based Carrefour (China) Group denies the accusation posted by a micro-blogger that its stores sell oilfish as cod, saying the cod for sale are silver pout and buffalo cod, species of cod family, and have proper certificates from import authorities.

Carrefour made the statement on its official micro blog at sina.com.cn after a post by netizen Triple Yan saying that toxic oilfish, banned in food markets in Europe, was sold in Carrefour labeled as cod was widely circulated.

The two fish species for sale in Carrefour have been licensed by the Entry-Exit Inspection and Quarantine Bureau - China's top entry-exit regulator, noted the company, urging "the whistleblower" to contact them and vowing to investigate into its supply chains in an effort to protect consumers' rights.

"Oilfish could also be regarded as a subspecies of cod, although edible, it is fat-rich and could cause physical discomforts like diarrhea for certain people," said Gu Zhenhua, deputy director of the Shanghai municipal food security regulator. He added that China has yet to have regulatory rules or ban on cod sale.