It is working with more than 400 brands to fight counterfeiters, and has a 150 million yuan fund that enables it to refund consumers who buy fake products.

Founded in 2015, Pinduoduo is the third-largest e-commerce platform in China, behind Alibaba Group and JD, and it has more than 300 million users.

Its focus on user recommendations and social networking to boost sales has set it apart from the traditional search engine model adopted by most e-commerce firms, such as Amazon and Alibaba. When it debuted on the Nasdaq in New York, its shares rose by more than 40 percent on the first trading day.

You Yunting, a lawyer and partner at DeBund Law Offices in Shanghai, said that as an online retailer, Pinduoduo should check the quality and authenticity of the products sold on its platform. It should also be held jointly liable for any infringements due to supervisory negligence, You said.

Chinese e-commerce majors, including Alibaba and JD, have stepped up efforts to crack down on counterfeit products sold by third-party vendors on their online marketplaces.

"We need to fight counterfeits the same way we fight drunk driving", said Jack Ma, the founder and chairman of Alibaba, in an open letter to the National People's Congress last year, asking lawmakers to bring in stricter punishments for manufacturers of fake goods.

More than 240,000 stores on Taobao, an online marketplace run by Alibaba, were closed last year on suspicion of intellectual property infringement, compared with 180,000 in 2016, according to Alibaba's 2017 annual report on intellectual property rights protection.

Ninety-seven percent of listings for counterfeits were deleted before transactions had taken place. The number of listed counterfeit goods removed was 27 times higher than the IP complaints filed by individuals or companies.

Zheng Junfang, Alibaba's chief platform governance officer, said: "Ninety-five percent of IP complaints were processed within 24 hours. Compared with 2016, the processing time has fallen by 68 percent."

Artificial intelligence and big data technologies have been used to deal with the counterfeiting problem.

Alibaba is working with the authorities to combat fake products. Last year, it helped the police to arrest 1,606 suspects and raided 1,328 locations where counterfeit goods were being made. The value of the fakes involved in these cases was estimated to be about 4.3 billion yuan.