HONG KONG — The Hong Kong government on Monday proposed legislation that would allow the city’s leader to designate certain criminal acts as national security offenses, stepping up its efforts to stamp out challenges to its rules in the city where critics say freedoms have been eroding.

After massive democracy protests rocked the Asian financial hub in 2019, Beijing imposed a national security law that has been used to arrest many leading activists. The city’s government in 2024 enacted another security law, targeting other crimes such as espionage and disclosing state secrets.

Critics said the two security laws have stifled the city’s Western-style civil liberties that Beijing had promised to maintain when the former British colony returned to Chinese rule in 1997. But the authorities insist the laws are crucial for the city’s stability.

In a document submitted to the legislature Monday, the Security Bureau and the Department of Justice proposed the subsidiary legislation to state clearly the classification mechanism for the term about “other offenses endangering national security under the law” of Hong Kong.

They said if the chief executive issues a certificate to ascertain that the act in a criminal offense case involves national security, then the case would fall into that category.

If a suspect is charged with a national security offense, but also faces an alternative charge for the same act, then that alternative charge will also be considered as an offense endangering national security, they said.

“Amid the present complicated geopolitical landscape, national security risks still exist. Stating clearly the above mechanism by way of subsidiary legislation can improve the legal system and enforcement mechanisms for Hong Kong to safeguard national security,” they said in the document.

The legislation was meant to refine details of procedural matters and bring greater certainty to the implementation of certain provisions, the authorities said.

“The subsidiary legislation does not involve the creation of any new criminal offense, penalty or enforcement power,” they said.

The government said the city should complete the legislative process “as soon as possible” and that it will finalize the proposed legislation after listening to the views of lawmakers. The legislation would take effect on the day when it is published in the government’s gazette.