The four had urged foreign governments to sanction China and Hong Kong over Beijing’s crackdown on dissent in the territory, heightening a conflict with Beijing over the semi-autonomous Chinese territory’s future.
The Communist Party accused Alvin Yeung, Dennis Kwok, Kwok Ka-ki and Kenneth Leung of violating their oaths of office.
Pro-democracy activists say China’s ruling Communist Party, which has tightened control in Hong Kong in response to demands for more democracy, is destroying the civil liberties and rights that were promised the territory when Britain returned it to China in 1997.
Britain regards the MPs' expulsion as the latest breach by Beijing of the Sino-British Joint Declaration on Hong Kong.
On Wednesday, Mr Xiaoming was summoned to the Foreign, Commonwealth and Development Office after Foreign Secretary Dominic Raab denounced the expulsions as a “clear breach” of declaration.
In response, Mr Liu tweeted: “The qualification of Hong Kong legislative council members is purely an internal affair of China.
“No foreign country has the right to intervene in the matter.”
A resolution passed this week by the Standing Committee of China’s National People’s Congress said that any politician who supports Hong Kong’s independence, refuses to acknowledge China’s sovereignty over the city, threatens national security, or asks external forces to interfere in the city’s affairs should be disqualified, effectively banning any pro-democracy candidates.
The pro-democracy camp criticised the move as an attempt to block them from winning a majority of seats in the legislature — which was a possibility in the election.
Earlier in the year, the four politicians were barred from seeking reelection in a vote originally scheduled for September.
The government eventually postponed the election by a year, citing coronavirus.
Also on Thursday, pro-democracy politicians in Hong Kong began resigning to protest against the expulsions of four other politicians.
The mass departure will leave Hong Kong’s legislature with just 43 legislators, 41 of whom belong to the pro-Beijing bloc.
This means that the legislature could pass bills favoured by Beijing with little opposition.
The 15 remaining politicians in the pro-democracy bloc had said on Wednesday they would resign en masse after China’s central government passed a resolution that led to the four politicians’ disqualification.
Most of the 15 members did not attend a regular session of the legislature on Thursday, and some later handed in resignation letters at the Legislative Council’s secretariat.
China sharply criticised the move.
Its Hong Kong and Macao Affairs Office called the mass resignation “an open challenge” to the authority of the central government and the Basic Law, Hong Kong’s constitution.
“If these politicians hope to use their resignation to provoke opposition and beg for foreign interference, they have miscalculated,” it said in a statement.
Wu Chi-wai, the head of the pro-democracy bloc, said the Chinese and Hong Kong governments were trying to take away the separation of powers in the city, since the ousting of the four members bypassed the courts.
“We lost our check-and-balance power, and all the constitutional power in Hong Kong rests in the chief executive’s hands,” Mr Wu said.
He said it was the end of the city’s “one country, two systems” framework under which Hong Kong enjoyed autonomy and freedoms not found on the mainland since it was returned to China in 1997.
Claudia Mo, a pro-democracy politician who also handed in her resignation, said: “We are quitting the legislature only at this juncture.
“We’re not quitting Hong Kong’s democracy fight.”
Earlier in the day, one of the pro-democracy members, Lam Cheuk-ting, unfurled a banner
from a balcony inside the Legislative Council building saying city leader Carrie Lam had brought disaster to Hong Kong and its people, and that her infamy would last ten thousand years.
Chinese foreign ministry spokesman Wang Wenbin on Thursday reiterated Beijing’s support for Hong Kong’s government in “fulfilling its duty according to the NPC Standing Committee’s decision”.
“No country will turn a blind eye to acts of betrayal of the country by public officials, including members of the Legislative Council, who break their oaths of office,” Mr Wang said at a daily news briefing.
Britain, the United States, Australia and the EU denounced China’s move.
In recent months, Beijing has increasingly clamped down on Hong Kong, despite promising when it took control in 1997 to leave the territory’s more open legal and economic systems intact for 50 years until 2047.
Beijing imposed a national security law in June that some have labelled draconian after anti-government protests rocked the city for months last year, and it has used it to crack down on opposition voices.
In response, the US levelled sanctions on several officials, including Carrie Lam.
Several Western countries have suspended their extradition treaties with the territory, and Australia and Britain have offered Hong Kongers easier paths to settle in those countries.