"The main reason is there is no freedom of literary creation in China," he said.

Culture was a political tool in authoritarian regimes such as China, he said. Under such a system, "true culture is almost impossible".

People working in the cultural sector, especially the outspoken ones, are often under strict government control, he said. Many writers are not allowed to publish their works, or are arrested for fabricated crimes, while some writers are forbidden from leaving the country.

Writer and political activist Liu Xiaobo , winner of the 2010 Nobel Peace Prize, has been imprisoned since 2009 for his role in drafting Charter 08. Signed by 1,000 people across the country, it calls for democracy and human rights in China.

"The arrest and imprisonment of Liu is wrong," said Sha, a signatory of Charter 08. "It highlights the importance of having democracy in China as soon as possible."

In an environment where culture is pressed into the service of politics, some writers will be silenced and prevented from publishing their works, Sha said. Others will find platforms overseas to express themselves.

Sha was born in Nanjing , Jiangsu province, and moved to Shanghai aged seven. He graduated from the East China Normal University, and did postgraduate studies at the Shanghai Theatre Academy in 1961. He joined the Shanghai People's Art Theatre in 1963 as a playwright and became its dean in 1985. He was appointed vice-chairman of the Shanghai Playwrights Association in 1991. Sha is currently honorary vice-chairman of the China Drama and Literature Society.

Many of his works are banned on the mainland, including one of his most controversial plays . Based on a true story, the play examines corruption within the Communist Party after the end of the Cultural Revolution. It opened to wide acclaim in Shanghai in 1979, but has never been officially performed on the mainland due to its critical take on the party.

, which focuses on the relationship between Jiang Qing and her husband Mao Zedong , was written in 1991 but only arrived in Hong Kong in 2010.

Sha said he was not discouraged by bans on his works on the mainland. "I am thankful for the [censorship] system," he said. "Dictatorship makes me independent; authoritarianism makes me devoted," he said.

Sha said writers had to guard their spiritual freedom. "No matter how cruel the suppression is, writers have to insist on writing what they want to express," he said. "The ones who should be fearful are not writers but those in power," he said. "History has shown that a dictatorship will always be eliminated in time."

Sha said there were signs of reform in the mainland's political system, citing the ideas of Guangdong party chief Wang Yang and the fall of former Chongqing party boss Bo Xilai .

Wang is widely seen as a reformist within the party. "We must abandon the idea that people's happiness is granted by the party and government," he said in May.

It would have been impossible to state such an argument previously on the mainland, Sha said.

Bo was removed from his post as Chongqing party secretary in March and later stripped of Politburo membership for "serious breaches of party discipline." He was said to have run roughshod over the rule of law in a controversial anti-triad campaign.

Although Bo's fall presented a crisis, Sha said it showed political reform was possible. "The fall of Bo has revealed a little crack in the iron wall," he said. It demonstrated that the unity and harmony the party has stressed as paramount had started to crumple, he added.

The public had grown intolerant of government corruption and ineffective anti-graft campaigns, he said. "There are voices within society that say it is imminent that China will change," he said.

Many mainlanders are taking to the internet to express their discontent, triggering an unprecedented response from the government to block information it deems undesirable. Sha said internet censorship was a feature of China "in transition" from an authoritarian regime to a more democratic political system.

"Now is the time when old things are not completely eliminated and new things have not yet emerged," he said. "But at least there are many open ideas on the internet."

The government has tightened its hold on the flow of news in the lead-up to the party's 18th national congress, at which new leaders will be chosen. Sha said it was hard to predict how Xi Jinpin and Li Keqiang , who are expected to take over as president and premier, will lead.

"I'm not familiar with the political figures in China. They dare not say in public what they really think," he said. "If the choice by the party is correct it will be good for the people; if not, it will be a disaster," he said.

"I hope Xi and Li can be more open than the current leaders and bring good change to China," he said. "But right now I remain cautious."