Justice Secretary Paul Lam on Wednesday said the Constitution provides the fundamental legal protection for the "One Country, Two Systems" framework, and people should start learning about the Constitution from a young age.

Addressing the flag-raising ceremony on Constitution Day, Lam said the event was established to promote constitutional spirit and the rule of law.

"Given the fundamental importance of the Constitution in implementing 'One Country, Two Systems' in Hong Kong, we must strengthen constitutional awareness. The prerequisite is to deepen public understanding and knowledge of the Constitution," he said.

"The activities on Constitution Day serve to promote and propagate the Constitution. It's also a good opportunity to promote rule of law awareness through public education."

The SAR should make full use of the unique advantages under "One Country, Two Systems" and safeguard national sovereignty, security and development interests, Lam added.

The justice chief also called it an "important mission" to teach youngsters about what the Constitution is and why it matters, adding that disciplinary services officers should stand at the forefront as guardians of the Constitution.

More than 100 members of the disciplined services took part in the flag-raising ceremony led by the Security Bureau at the Hong Kong Customs College.