The UK's offer was made in July when Beijing imposed a strict national security law on the former British colony.

Critics say it undermines the civil freedoms that China agreed to uphold when Hong Kong was handed back in 1997.

Beijing has previously warned the UK not to meddle in "domestic issues".

Friday's warning came from the Hong Kong arm of China's Foreign Ministry.

The British offer is not for all residents of Hong Kong, but only those holding a British National Overseas (BNO) passport. Only those born before the 1997 handover of the territory to China have the right to hold one.

Around 300,000 people currently hold a BNO passport, while an estimated 2.9 million people are eligible for it, according to the British Consulate General in Hong Kong.

UK government analysts estimate that up to one million people could take up the offer to live in the UK when the new visa becomes available in January.

However, critics say the new visa law won't protect young pro-democracy protesters who were born after 1997 and are primarily targeted by the security law.

The law which targets secession, subversion and terrorism with punishments of up to life in prison, was introduced in July, in response to repeated protests in Hong Kong demanding more democracy and less Chinese influence.

That same month, UK Home Secretary Priti Patel said Hong Kong's British National Overseas (BNO) passport holders and their immediate dependants would have the right to apply for a special UK visa from January.

BNO holders already have the right to visit the UK visa-free for six months.

The new offer however will allow them to remain in the UK for a longer period, and then eventually become full British citizens.