Ai Weiwei, the internationally renowned Chinese artist, has told Al Jazeera that a  $2.3m tax bill and investigations into his financial affairs are part of a politically motivated campaign against him, and pledged to continue to speak out.

Ai, who has become one of the most prominent critics of China's ruling Communist Party and part of a growing dissent movement , said that speaking out had become "some kind of responsibility".

Despite his own personal fears, Ai said in a telephone interview that "the only thing that can help me is to let the truth out".

Ai, who spent 81 days in detention earlier this year, said it was especially important for him to speak out because he was only one out of "so many [other] people who are scared and ... will never be heard", referring to others who have criticised China's policies in the past.

Ai said the allegations against him were not about money, but the current state of the Chinese justice system.

"It's the issue of how a state can survive when they are not respectful of the law, when they're clearly don't have a clear procedure, transparency, or public discussion."

Describing his interrogation while in detention, Ai said that the details of the allegations against him were not discussed, instead "they questioned me about subversion of state power".

Ai said he had been given no account statements to corroborate the allegations against him. He maintains he was not a manager at the Beijing Fake Cultural Development Ltd, the company under investigation which handles Ai's financial affairs.

Ai said his interrogators had "clearly told me that the tax charge was to have people think that I'm a bad man - that if you criticise the government, then we have to teach a lesson".