BEIJING, Aug 18 (Reuters) - Hosts in China"s livestreaming industry should speak Mandarin and dress appropriately when they market products online, the country"s commerce ministry said on Wednesday, as it looks to tighten its oversight of the sector. Livestreaming marketing has seen its popularity surge in the last two years among brands like L’Oreal, Nike, Dyson and online shoppers, and most Chinese e-commerce platforms now offer the option to purchase and sell products via livestreaming. It became the target of scrutiny last year with some shoppers and brands accusing some livestreamers of misrepresenting products or faking sales numbers, prompting China"s cyberspace regulator to announce draft rules in November. China"s Ministry of Commerce on Wednesday published more detailed guidelines and for the first time mentioned a preferred language. Mandarin is the official medium in China but there are also many dialects and ethnic minority languages in the country. "It is better to use Mandarin during livestreaming," it said in a section about how livestreamers were expected to behave. The new rules, which are up for public review until Sept. 2, also said livestreamers should dress in a way that is inoffensive to their audience, and carry an image reflecting the characteristics of the products or services they try to sell. Reporting by Beijing Newsroom; Editing by Bernadette Baum Our Standards: The Thomson Reuters Trust Principles.