Prominent Hong Kong democracy advocate and newspaper publisher Jimmy Lai has again been denied bail ahead of his April trial on charges of colluding with foreign forces.

Lai is one of several activists facing charges and possibly lengthy prison terms under the sweeping National Security Law that Beijing imposed on the semi-autonomous southern Chinese city last year following massive anti-government protests in 2019.

Critics at home and abroad say the legislation amounts to a crackdown on political dissent and free speech that is eroding the rights and freedoms promised to Hong Kong under the “one country, two systems” framework following the handover from British colonial rule in 1997.

Arrested and charged in early December, Lai was at first denied bail then granted it on appeal under strict conditions amounting to a form of house arrest.

That prompted a withering attack on the Hong Kong judiciary by the ruling Communist Party newspaper People’s Daily.

Lai was then returned to prison under a provision of the law that allows a judge to deny bail in cases where the person may again commit the crime for which they are already facing charges.

Lai’s latest appeal on Thursday to Hong Kong’s High Court was based on separate legal grounds.

He also faces fraud charges related to the use of office space by his Apple Daily newspaper and other media holdings, which reported he was also arrested on Wednesday on suspicion of aiding dissidents to flee Hong Kong.

Along with Martin Lee, an 82-year-old veteran of Hong Kong’s democracy movement, Lai is one of the most senior critics of the current Beijing-backed government and has long faced legal and commercial retaliation for his statements and activism.