Beijing’s authorization of the expulsion of elected legislators from Hong Kong’s parliament constitutes “a clear breach” of the 1984 joint UK-China declaration, Raab said.

According to the document, Hong Kong would maintain a “high degree” of autonomy in its domestic affairs. This was a key condition under which the UK returned the city, its colony at the time, to China in 1997.

“The UK will stand up for the people of Hong Kong, and call out violations of their rights and freedoms. With our international partners, we will hold China to the obligations it freely assumed under international law,” Raab said.

The UK’s Foreign Office stated that China previously violated the same pact in 2016 and last year when it passed a law that was aimed at maintaining security in Hong Kong and criticized by local activists.

It added that the actions against the legislators were “part of a pattern apparently designed to harass and stifle all voices critical of China's policies.”

Minister of State for Asia Nigel Adams said that the government will consider targeting Chinese officials under a “Magnitsky-style sanctions regime,” referring to a US law which allows for blacklisting foreigners accused of human rights violations.

On Wednesday, China’s top legislature in Beijing passed a resolution that gave Hong Kong's government power to immediately expel individual members of the city's Legislative Council accused of promoting independence from China and inviting foreign meddling.

Four opposition MPs were ousted the same day. Fifteen remaining opposition lawmakers jointly resigned in protest, arguing that the dismissal of their colleagues was undemocratic and had violated local laws. The head of the city's government, Carrie Lam, meanwhile, insisted that the move was legal and necessary.

Beijing has long been accusing foreign countries of stoking protests and inciting riots in Hong Kong. Chinese Foreign Ministry spokesperson Wang Wenbin told reporters that giving the city government powers to unseat MPs it deemed disloyal was necessary to uphold the rule of law and maintain security.

On Thursday, China’s agency responsible for Hong Kong affairs blasted the mass resignation of opposition MPs as a “farce” which highlighted how some lawmakers “disregard citizens for their own political interests.”

“It shows their stubbornly confrontational attitude against the central government,” the statement read.