LONDON • Britain said China's imposition of a security law on Hong Kong was a "clear and serious" violation of the 1984 Joint Declaration and that London would offer around three million residents of the former colony a path to British citizenship.

"The enactment and imposition of this national security law constitute a clear and serious breach of the Sino-British Joint Declaration," Prime Minister Boris Johnson told Parliament yesterday.

Mr Johnson said Britain would stand by its pledge to give British National (Overseas) passport holders in Hong Kong a path to British citizenship, allowing them to settle in Britain.

Almost three million Hong Kong residents are eligible for the passport. There were 349,881 holders of the passports as of February.

Hong Kong's autonomy was guaranteed under the "one country, two systems" agreement enshrined in the Sino-British Joint Declaration signed by then Chinese Premier Zhao Ziyang and then British Prime Minister Margaret Thatcher.

Foreign Secretary Dominic Raab said Britain had carefully assessed China's national security legislation since it was published late on Tuesday. "It constitutes a clear violation of the autonomy of Hong Kong, and a direct threat to the freedoms of its people, and therefore I'm afraid to say it is a clear and serious violation of the Joint Declaration treaty between the United Kingdom and China," Mr Raab said.

The authorities in Beijing and Hong Kong have repeatedly said the law is aimed at a few "troublemakers" and will not affect rights and freedoms, nor investor interests.

United States Secretary of State Michael Pompeo said Hong Kong can no longer be considered sufficiently autonomous, and US President Donald Trump is considering revoking some or all of its special trade privileges.

"A free Hong Kong was one of the world's most stable, prosperous and dynamic cities," Mr Pompeo told reporters in Washington yesterday. "Now it will be just another communist-run city where its people will be subject to the party elite's whims. It's sad."

European Union foreign policy chief Josep Borrell yesterday said it was essential that existing rights remain observed in Hong Kong.

"The European Union considers it essential that the existing rights and freedoms of Hong Kong residents are fully protected," Mr Borrell said in a statement.

These include "freedom of speech, of the press and of publication, as well as freedom of association, of assembly, of procession and of demonstration", the statement added.

Meanwhile, the G-7 group of nations has said the law would jeopardise a system "which has allowed Hong Kong to become one of the world's most prosperous regions".

REUTERS, AGENCE FRANCE-PRESSE, BLOOMBERG