An outspoken political philosopher and government critic has been thrown out of the mainland's largest think tank, allegedly for publishing a series of articles calling for constitutional reform. Zhang Boshu has been given three months to transfer out of the state-sponsored Chinese Academy of Social Sciences, ostensibly for taking two months' 'absence without leave'. However, the scholar contends that two unauthorised breaks in question were study trips to universities in Japan and the US in July and August, for which the academy declined him permission as he intended to discuss political topics that were 'excessively sensitive'. 'Of course I could not comply with such absurd and unreasonable decisions,' Zhang said in a statement released through New York-based Human Rights in China. Zhang said he believed the reason for his transfer was that he had not observed 'norms of political discipline' stipulated by the academy's Communist Party committee. 'I have published a large amount of essays, books and opinions during the past few years which have criticised China's current political system, and I have advocated and pushed for reform of China's constitutional government,' he said. 'In the eyes of the conservative leaders of the academy, I have clearly violated the aforementioned political discipline.' Zhang, 44, joined the academy in 1991 and has been a vocal critic of government policy, including the 1989 Tiananmen crackdown. The academy laid down its decision in a three-paragraph statement dated December 15 but handed to Zhang on Monday. The judgment said that Zhang had 'repeatedly violated work discipline, leaving the country on his own initiative, without asking for leave or receiving permission'. It said this was in contravention of internal regulations. However, Zhang said he rejected the academy's decision and insisted he would resist attempts at 'sweeping [him] out the door'. 'The Chinese Academy of Social Sciences is an academic institution that depends on public financing and it is the post where I can best develop my knowledge and abilities, and where I can make a contribution to the development of our country and the advancement of our nation,' he said.