The Hong Kong government has told some foreign consulates to stop accepting a British travel document many of its young people use to apply for working holiday visas in Europe, North America and parts of Asia.
In a move seen by some as a diplomatic affront, Hong Kong informed about a dozen consulates by letter on Thursday it no longer considered the British National Overseas passport a valid document as of January 31.
The letter demands its Hong Kong passport should be used instead.
A diplomatic row broke out over the BNO in January after Britain introduced a new visa scheme offering a pathway to full citizenship for Hongkongers who want to leave the Chinese-ruled territory.
Britain launched the scheme after Hong Kong passed a sweeping national security law last year, that critics say is crushing dissent in the former British colony.
Almost three million Hong Kong residents hold or are eligible for the BNO document, created ahead of Britain handing the city back to Chinese rule in 1997.
Hong Kong also started to mirror mainland China by not recognising dual nationality, preventing for the first time foreign diplomats from visiting locals with foreign passports in detention.
"Most countries are going to ignore this," said one senior Western diplomat.
"It is the Hong Kong government just trying it on ... they have no right to tell any state what foreign passports it can recognise."
Another envoy described the move as "bordering on belligerent" and said it was not the way Hong Kong, generally mindful of the city's standing as an international financial hub, has traditionally behaved.
A Hong Kong government website lists 14 countries under the reciprocal Working Holiday Scheme, including Japan, Canada, Germany, Britain and Australia.
Officials in Japan, South Korea, Italy and New Zealand confirmed they still recognise the BNO passport.
South Korea's Foreign Ministry added that it had not received the letter while Hungary said it had, and had started talks to change the working holiday program.
Other nations, including the United States, Finland and Norway, also offer similar arrangements or student exchanges for Hongkongers, and have accepted BNOs from applicants.