The Chinese Embassy is urging "the New Zealand side" to "stop interfering in Hong Kong affairs" after the Government joined the global backlash against a new security law.
Beijing passed the legislation on Tuesday, bypassing the city's local Parliament, which New Zealand politicians have suggested breaks the 'one country, two systems' framework Hong Kong has been operating under.
A statement released by Foreign Minister Winston Peters on Wednesday said the Government is expressing "deep disappointment" at the passage by China's National People's Congress Standing Committee of the new law.
The Chinese Embassy has responded by telling New Zealand to "stop interfering in Hong Kong affairs and China's internal affairs, and do more to promote the sound and steady development of the China-New Zealand relations".
The new law allows extradition to the Chinese mainland for trial. It punishes crimes of separatist activity, state subversion, terrorist activity and collusion with foreign forces, which can be punishable by up to life in prison.
More than 300 people were arrested in Hong Kong on Wednesday as protesters took to the streets in defiance of the law, international media reported. Police used pepper spray and fired pellets at protesters as crowed chanted "resist till the end".
Peters said the New Zealand Government is expressing "serious concern" about the "imposition of this legislation on Hong Kong without inclusive consultation or the proper involvement" of all of Hong Kong's institutions.
"We share the international community's stake in preserving the high degree of autonomy and freedom available to Hong Kong and its people under the 'one country, two systems' framework," he said.
"It is this autonomy and freedom, together with open governance, judicial independence, and consensus on the rule of law that have been fundamental to Hong Kong's growth as a global financial and economic hub since 1997."
The UK's ambassador to the United Nations Julian Braithwaite has delivered a joint statement on behalf of 27 countries - including Australia and New Zealand - expressing concern over the new law.
Prime Minister Jacinda Ardern said New Zealand shares the position of its Five Eyes partners, a security alliance that includes the US, UK, Canada and Australia.
"Sometimes you'll see collective statements, sometimes you'll see singular," she said on Tuesday. "You'll see the same messaging and very little difference between the Five Eyes partners and the positions we've all taken on this issue."
Hong Kong, officially named the Hong Kong Special Administrative Region of the People's Republic of China, was returned to Beijing from Britain in 1997 under the 'one country, two systems' approach.
The Chinese Embassy insisted the "legislation for safeguarding national security" in Hong Kong is "purely China's internal affair" and said it "firmly opposes any foreign interference in China's internal affairs and Hong Kong affairs".
It said opinion was "drawn extensively" from the people of Hong Kong on the new law, which is said is a "fundamental solution" for Hong Kong to restore "order, end chaos and resume stability".
International visitors to Hong Kong - including New Zealanders - will be better off because of the new law, and it will "only target very few criminals", the embassy added.
"Its implementation will strengthen Hong Kong's legal framework, better protect the basic rights and freedom of the people in Hong Kong, ensure social order, improve business environment, and benefit Hong Kong citizens and international investors including those from New Zealand."
Waikato University Professor of Law Al Gillepsie said it is "pointless" to question whether China has acted wrongfully with regards to the 1997 agreement.
He said it cannot be tested in a court of law - like the International Court of Justice - because China would not show up or would veto the debate.
China said the legislation was necessary after sometimes violent anti-government and anti-Beijing protests rocked the city since June last year.
Hong Kong police arrested 15 pro-democracy activists at the time, including Democratic Party founder Martin Lee and trade union leader Lee Cheuk-yang. They were charged with offences including organising and joining "unlawful assemblies".
Damaging certain transportation vehicles and equipment will now be considered an act of terrorism, and anyone convicted of violating the new security legislation will not be allowed to stand in any Hong Kong elections.