HONG KONG (Reuters) – A group of 86 non-government organisations issued a joint letter on Wednesday asking Chinese authorities to scrap plans to introduce national security legislation in Hong Kong, saying it threatens basic rights and freedoms.

The letter, signed by Amnesty International, Human Rights Watch and Freedom House, among others, was addressed to Li Zhanshu, Chairman of the Standing Committee of the National People’s Congress, China’s top legislative body.

Beijing last month announced a plan to introduce legislation in Hong Kong to tackle secession, subversion, terrorism and foreign interference. The law could see Chinese security agencies set up bases in the city for the first time.

Critics, including diplomats, lawyers and business executives, see the law as a threat to a “one country, two systems” formula, agreed when the former British colony returned to Chinese rule in 1997 to protect its freedoms and role as a global financial centre.

Hong Kong and Beijing officials say the planned law in fact strengthens the governance formula and would only target a small number of “troublemakers” threatening national security, while leaving rights and freedoms intact.

They have dismissed criticism from foreign governments and organisations, urging them to stop interfering in China’s internal affairs.

Key details of the legislation, expected to be implemented by September, remain unknown.

“Although no details of the law’s contents have been made publicly available, the decision – along with recent comments by Chinese and Hong Kong officials – suggest that it will threaten the basic rights and freedoms of the people in Hong Kong,” the letter said.

“We are particularly concerned about the law’s impact on Hong Kong, especially its vibrant civil society.”

Hong Kong leader Carrie Lam on Tuesday urged opponents of Beijing’s national security legislation plans to stop “smearing” the effort, saying those who did were “the enemy of the people”.

The signatories of the letter included rights groups from the United States, Australia, Canada, Hong Kong, Taiwan and Europe.