The 30 strong group representing the interests of women, workers, community and ethnic minorities, staged a protest before marching to central government offices to deliver a petition.
The group said in a statement it strongly opposed the government's moves to implement the laws it has been obliged to introduce since returning to Chinese rule as the Special Administrative Region (SAR) five years ago.
"We are deeply concerned that through enacting such legislation, the SAR government would introduce into Hong Kong the mainland practice of using "national security" as a pretext to silence different opinions, suppress the development of our civil society and deprive Hong Kong people of their basic human rights protection," it said in a statement.
Justice Secretary Elsie Leung told reporters last week "it is about time" to enact the law which would punish offences against the state.
Her remarks followed reports that a consultation paper on the issue would be issued as early as next month.
The group, which included the Asian Human Rights Commission, added the implementation of the law under Article 23 of the Basic Law -- Hong Kong's mini-constitution -- would create a "white terror" and its "chilling effects" would pose a serious threat to the freedoms of thought, belief, the press and speech.
It also said reports that the government had allegedly held secret discussions with Beijing about the legislation prior to holding consultations with the Hong Kong people were "problematic and disturbing".
"We deeply regret that such an approach goes against the principle of what is stated in Article 23 of the Basic Law, that Hong Kong shall enact such laws on its own. It also violates the principle of high degree of autonomy."
Leung last week denied reports that Beijing had pressured the government to enact the law, which critics say will allow authorities to clampdown on dissidents.
"I don't know of any Beijing timeframe or pressure to enact the law as soon as possible," she said.
Under the Basic Law the government is obliged to enact laws prohibiting treason, sedition, subversion, secession and the theft of state secrets.
Senior Chinese officials led by Vice Premier Qian Qichen, who is responsible for Hong Kong affairs, have told the territory to enact the subversion law as soon as possible.
But some legislators fear such laws could run counter to Hong Kong's policies on freedom of speech and have argued that prohibition of treason and subversion are covered by existing legislation.
In July the territory's Bar Association said Hong Kong did not need a new subversion law as existing legislation already covered sedition and treason.
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