China must open its doors to European business or face a protectionist backlash, European Union Trade Commissioner Peter Mandelson is expected to warn Beijing today at an EU-China trade conference in Brussels. "Protectionist voices will be raised and if the public perception is that China is closed to our trade while benefiting from our openness, then they will be impossible to silence," he is expected to say, the Financial Times reported. Mandelson is particularly concerned about the protection of European intellectual property rights in China, and the access of EU companies in sectors such as construction, banking and insurance. "Too often Europe's businesses meet a Chinese wall rather than an open door," he is expected to say. Meanwhile the Commission has proposed anti-dumping duties for plastic bags from China, which are worth an estimated US$300 million a year.