While highlighting positive developments in the China market, Ng said that Hong Kong filmmakers are 'worried that they're gaining the China market at the expense of losing the Hong Kong [filmmaking] style'.
The issue has long been a problem for Hong Kong, which depends on the mainland market but is prevented from making certain types of films,including crime thrillers and horror movies, by China's censorship rules.
'We need to have different policies so that the vitality of free thinking can be maintained in co-production projects,' said Ng, who set up the first co-productions with China when the country opened after the Cultural Revolution.
While China has loosened some of its co-production requirements - including the proportion of mainland talent in each film - it appears to have tightened its censorship rules since the end of last year. However, the Film Bureau under the State Administration of Radio, Film and Television (SARFT) maintains that it has simply reinforced existing guidelines.
Indeed, Ng's comments drew a fast response from Film Bureau deputy director Jiang Ping, who retorted that policy has been consistent and more dialogue is needed so that Hong Kong filmmakers can understand how to work within the rules.
'Some people are concerned that the [censorship] policy was tightened in 2008, but that is due to a lack of communication,' Jiang said. 'We need to talk to filmmakers in Hong Kong and Taiwan to discuss which films are suitable for co-production.'
He added that some Hong Kong filmmakers 'are not fully aware of what the mainstream themes are in mainland China'.
Apart from Ng's comments, there was no other mentionat the seminar of China's current censorship climate. Panelists including Japanese producerSatoru Iseki and Red Cliff producer Terence Chang talked instead about the advantages of pan-Asian co-production, including the ability to increase budgets and arrange a day-and-date multi-territory release.
Jason Reed, who oversees local co-production for Disney as executive vice president of Walt Disney Studios Motion Picture Production, explained that his studio is taking the long-term approach to working with China by establishing a content creation centre in Hong Kong.
'We have a responsibility both to local cultural heritage and to the Disney brand to build long-term relationships in the region,' Reed said.
Projects in development at the Hong Kong production office include a kung-fu reworking of Snow White And The Seven Dwarves and a Chinese version of High School Musical.
Panelists also spoke of improvements to the China market - Ng praised the introduction of revenue-sharing agreements while Chang talked of his successful collaboration with China Film Group on Red Cliff.
Iseki observed that the growth of China's box office has made it possible to raise finance for big-budget movies - such as his 2006 production Battle Of Wits - from Asia alone. He also highlighted that China is a good source of material.
'I decided to come here, not because it's a big market, but because there are a lot of good stories in China,' Iseki said. 'We should work hard to understand one another.'
But the seminar made it clear that while China may be open for business, the authorities still find it difficult to discuss censorship issues in an open forum. Unlike at other seminars at the Shanghai film festival, guests at the co-production panel were not given the opportunity to ask questions from the floor.