China has asked Britain to “rectify its mistakes immediately” as Britain reaffirmed its plan to provide British citizenship avenues to the nearly three million people living there.
The offer was made in July when Beijing imposed a strict national security law on the former British colony.
Critics say it undermines civil liberties, which China agreed to hand back to Hong Kong in 1997.
Beijing has previously warned the UK to ignore “domestic issues”.
Friday’s warning came from the Hong Kong branch of China’s foreign ministry.
The British offer is not for all Hong Kong residents, but only for those holding British National Overseas (BNO) passports. Only those born before China were ceded to the region in 1997 have the right to keep one.
According to the British Consulate in Hong Kong, around 300,000 people currently hold a BNO passport, while an estimated 2.9 million people are eligible for it.
UK government analysts estimate that up to a million people can take up the offer to stay in the UK if a new visa becomes available in January.
However, critics say the new visa law will not protect young pro-democracy protesters, who were born after 1997 and are primarily targeted by the security law.
Legislation targeting segregation, sabotage and terrorism was introduced in July, with repeated protests in Hong Kong and life sentences in prison demanding greater Chinese influence.
In the same month, UK Home Secretary Preeti Patel said that Hong Kong’s British National Overseas (BNO) passport holders and their immediate dependents would have the right to apply for a special UK visa from January.
BNO holders already have the right to travel UK visa-free for six months.
However the new proposal would allow them to remain in Britain for longer, and then eventually become full British citizens.