Security Secretary Chris Tang on Wednesday brushed aside suggestions that proposed national security legislation under Article 23 of the Basic Law does not go far enough in dealing with people who harass officers handling these types of cases.

Under the proposal, such harassment will only constitute an offence if the officer is alarmed, and if the person involved acted unreasonably.

At the Legco committee scrutinising the bill, Business and Professionals Alliance lawmaker Lo Wai-kwok said the government was being "too merciful", but Tang disagreed.

"Let's look at the intention and whether the person has achieved the purpose of intimidating someone and whether the other person is alarmed," he said.

The security minister said an unreasonable action may become reasonable in a different scenario. For example, he said it may be reasonable for a man to use abusive language against a security officer if that is the way he normally talks.

"So we believe we have laid down fair criteria, and we are offering suitable protection for people working on national security cases. At the same time, we also ensure that people without the criminal intent will not get caught inadvertently."

The draft legislation also stipulates that national security inmates cannot be released early if the Commissioner of Correctional Services believes they would continue to undermine national security.

The acting law officer of the Department of Justice, Daphne Siu, said it is not a right but a discretionary treatment for inmates to have their sentences remitted.

She added that inmates could always submit their views if they do not agree with the commissioner's decision, which is subject to judicial review.