A leading Chinese economist at a government thinktank has reportedly disappeared after being disciplined for criticising Xi Jinping in a private chat group.

Zhu Hengpeng, 55, is believed to have made disparaging remarks about China’s economy, and potentially about the Chinese leader specifically, in a private WeChat group. Zhu was subsequently detained in April and put under investigation, according to the Wall Street Journal which cited anonymous sources.

Zhu worked for the Chinese Academy of Social Sciences (Cass) for more than 20 years, most recently as the Institute of Economics deputy director and director of the Public Policy Research Center. He has reportedly not been seen in public since April when he spoke at an event organised by Chinese media outlet Caixin, which he had done previously. Efforts by the Wall Street Journal to contact him at home were unsuccessful. The Cass has not responded to queries from the Guardian.

Earlier this month Hong Kong media reported a shakeup of the institute’s senior ranks, with the director and secretary also removed from their posts at the same time Zhu was stripped of his role. The other two officials were reassigned, according to Sing Tao Daily, but Zhu was not, and is no longer listed on the Cass website. Websites related to his work at Tsinghua University have also been taken offline, although the Guardian could not confirm when.

The Cass is a leading thinktank in China, which reports directly to the cabinet of the Chinese Communist party (CCP), the State Council, and has long been an influential policy advisor, sometimes providing relatively frank analysis. However under the increasingly authoritarian rule of Xi, criticism of the CCP and his individual leadership has become increasingly frowned upon, and treated punitively.

China-based academics have previously told the Guardian of a growing fear among their profession of reporting or discussing negative assessments of China’s economic, social, or political situation for fear of reprisals. Discussion of Xi as an individual, especially in online spaces which are censored and monitored, is largely avoided or done through vague or coded statements.

Notices on the Cass website show staff engaging in several political education sessions in recent months, with a heavy focus on party loyalty and adherence to Xi Jinping Thought – the name given to the enshrined political ideology of the CCP leader.

“The meeting emphasised that we must always bear in mind that the Chinese Academy of Social Sciences is a political institution whose work is centred on scientific research, put strict enforcement of the party’s political discipline first, work hard to enforce strict discipline and abide by rules,” said a report on one July meeting, led by Cass president Gao Xiang. Gao, a Xi loyalist, was appointed to the role in 2022 and has overseen a campaign to improve party loyalty at the institution.

The specifics of what Zhu wrote in the private WeChat group are not known, although Sing Tao Daily described it as “improperly discussed central policies”. The Wall Street Journal also reported he allegedly made a reference to “Xi’s mortality”.

China’s economy is struggling, and there are concerns that the world’s second-largest economy will miss its own 5% annual growth target, a relatively modest ambition by historic standards. On Tuesday the country’s central bank announced the biggest stimulus efforts in years in a bid to boost growth, but experts expressed concern the measures, including a cut in interest rates, would not be sufficient.

A growing crisis in China’s property market has unfolded since authorities cracked down on excessive borrowing by developers, leading many to default on their debts. Property developers and owners continue to cope with high mortgage payments, dragging on their ability to invest and grow.

Regulators have avoided making large-scale cuts to borrowing costs, fearing that the stimulus would reignite a boom in sales and values, creating a fresh property bubble.

Additional reporting by Phillip Inman