An activist hospital worker was sent back to jail to await a subversion trial after a magistrate found she had breached the stringent bail conditions imposed on her under Hong Kong’s national security law.

Winnie Yu Wai-ming was escorted in a police van to West Kowloon Court on Tuesday, where prosecutors sought to have her bail revoked on the grounds she had again committed acts that had endangered national security.

The 34-year-old hospital clerk is one of 47 opposition figures facing subversion charges over an unofficial primary election in 2020 aimed at picking candidates for the postponed Legislative Council election.

She is the founder and former chairwoman of the Hospital Authority Employees Alliance, a union that emerged from the anti-government protest movement in 2019.

Yu was detained when she reported back to Sha Tin Police Station on Monday following a complaint lodged to the force.

Winnie Yu, the founder and former chairwoman of the Hospital Authority Employees Alliance, leaves the High Court.

Acting chief magistrate Peter Law Tak-chuen said Yu had violated her bail conditions by committing acts which could “be regarded on reasonable grounds as constituting an offence endangering national security”.

Details of the breach were subject to reporting restrictions.

Defence lawyers sought a second chance for their client by suggesting more stringent bail terms, but the magistrate refused.

After the hearing, Yu said to the public gallery: “Help me take care of my cats.” Some spectators chanted words of encouragement before Yu was taken away by prison officers.

She is allowed to renew her bail application in the High Court.

Yu last appeared at a public event in February, when she sold handicrafts and ground coffee in a Lunar New Year bazaar in Mong Kok. She told reporters at the time that she would use the profit from the sales to pay for living expenses and legal fees relating to the coming trial.

The accused won bail in the High Court last July, where it was set at HK$100,000 (US$12,793) as well as a HK$50,000 surety to be paid by her husband. She had previously spent nearly five months in custody.

Madam Justice Esther Toh Lye-ping had imposed a travel ban and a daily curfew between midnight and 6am on Yu. She was also ordered to surrender all travel documents and report to police four times a week. The judge warned the accused to refrain from engaging in all acts and speech that could endanger national security.

The High Court had previously granted bail to 15 defendants in the subversion case subject to a list of stringent conditions, but recent developments showed they remain closely watched by authorities after their temporary release.

The same magistrate in January denied bail to activist Owen Chow Ka-shing, who was among the 15 released, after prosecutors accused him of violating the terms.