Beijing's ambassador to London on Monday accused Britain of "gross interference" in China's internal affairs" over its response to a controversial national security law in Hong Kong.
The UK government has said it will offer Hong Kong residents a broader path to citizenship in response to the sweeping new security law for the former British territory.
The move could pave the way for more than three million Hong Kongers to move to Britain.
But Chinese ambassador Liu Xiaoming said Beijing has expressed its "grave concern and strong opposition" to the proposals, arguing that London has "no sovereignty, jurisdiction or rights of supervision over Hong Kong".
"These moves constitute a gross interference in China's internal affairs and openly trample on the basic norms governing international relations," he told reporters.
China last week enacted the sweeping security law for the restless city of around 7.5 million people, banning acts of subversion, secession, terrorism and collusion with foreign forces.
The legislation, which has sent a wave of fear through the territory, has criminalised dissenting opinions such as calls for independence or autonomy.
Britain is among the Western nations moving to offer millions of Hong Kongers refuge in response.
London has said it has a duty of care to residents of a colony it handed back to China in 1997, under an agreement designed to preserve its autonomy and freedoms for 50 years.
Prime Minister Boris Johnson told parliament last week he will allow anyone with British National (Overseas) (BNO) status -- and their dependents -- to come to Britain and eventually receive citizenship.
About 300,000 Hong Kongers have BNO passports and another 2.6 million are eligible to apply.
However, Foreign Secretary Dominic Raab conceded last week that Britain may be powerless if China moves to prevent a mass exodus.
Johnson's spokesman reiterated Monday that the law was "a clear and serious breach" of the 1984 Sino-British joint declaration governing Hong Kong's return to Chinese rule.
"We said we would make changes to the immigration rights of BNOs if China implemented this legislation and we have delivered on that promise," he added.
Liu said Beijing was mulling what reciprocal actions to take.
"We have to wait and see. We have to decide our counter-measures in accordance what the actual actions [are] to be taken by the British side," he added.
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)
