Passing the national security legislation required under Article 23 of the Basic Law was a "constitutional responsibility", Secretary for Security Lai Tung-kwok said yesterday.
But Lai said it should begin only at the appropriate time, and the social and political conditions would be considered before a decision was made.
He made the remarks while attending a passing-out parade for new graduates of the Police College in Wong Chuk Hang.
On Thursday, Zhang Xiaoming, head of the central government's liaison office, said the law should not be regarded as taboo.
Article 23 of the Basic Law states that it shall enact laws to prohibit any act of treason, secession, sedition or subversion against the central government. Hong Kong shelved a move to pass such laws in 2003 after half a million protesters took to the streets. Since then, it has remained a sensitive topic.