“[Beijing’s ruling] has made it very clear that the criteria for anyone who has taken an oath and served as a legislative councillor but thereafter they have engaged in activities which are breaching those requirements, is that they should immediately lose their qualification,” she said.

Lam said the NPCSC’s decision did not mean she now had additional powers to unseat legislators.

Officials such as electoral officers, the justice minister, the Legco president and the courts would still need to follow existing constitutional and election laws, she said.

“Hong Kong is a society under the rule of law … It’s not only the executive branch which has a say,” Lam said.

With no opposition lawmakers left in the city’s legislature, Lam’s planned legislative amendments could have far-reaching implications for the city’s political and electoral systems, commentators said.

Making good on a threat they had issued on Monday, Democratic Party chairman Wu Chi-wai said all 15 remaining pan-democratic lawmakers would tender their resignations on Thursday.

But pro-establishment lawmakers said that the pan-democrats had only themselves to blame, and that Beijing’s decision would ensure Hong Kong’s prosperity and stability.

They said the remaining 41 members from their camp would “act more diligently” to monitor the government, dismissing critics’ warnings that Legco would be reduced to a compliant “rubber stamp”.

“If the council turns quiet [without the opposition], the remaining lawmakers will be able to scrutinise government proposals in a more critical and careful manner,” said the camp’s leader, Martin Liao Cheung-kong.

What might lie ahead if Beijing moves to disqualify Hong Kong lawmakers

Independent lawmakers Cheng Chung-tai and Pierre Chan will also remain in Legco.

The NPCSC resolution stipulated that lawmakers would lose their seats if they were deemed to have promoted or supported the notion of Hong Kong independence and sought foreign intervention in the city’s affairs.

“This decision applies to lawmakers whose candidacies were invalidated during the nomination period of the Legco election originally slated for September 6,” the resolution stated, in a reference to the four disqualified pan-democrats.

NPCSC chairman Li Zhanshu, China’s third-ranking state leader, issued a statement saying the decision was “necessary and appropriate”.

“This is another important piece of legislation, as the standing committee insists on the ‘one country, two systems’ principle and improves its systems to protect national security,” he said.

In separate statements, the State Council’s Hong Kong and Macau Affairs Office (HKMAO) and Beijing’s liaison office in Hong Kong expressed firm support.

Quoting late paramount leader Deng Xiaoping, the HKMAO said: “Deng had pointed out that [the principle of] ‘Hong Kong people governing Hong Kong’ has its bottom line and standard, which is that patriots must form the main body of the city’s administrators.”

The liaison office also condemned the pan-democrats’ plan to quit as “irresponsible”.

Lam said on Wednesday that her government would amend local laws next to ensure they aligned with both the 2016 interpretation and the latest ruling from Beijing.

“It could involve specifying the formalities of oath-taking, who oversees it, as well as the mechanism and consequences of a breach of the oath,” she said.

In July, Lam suggested that there was no “legal basis” to stop the four lawmakers from serving out their extended term, even after they were banned from running for re-election, as she sought Beijing’s approval for the Legco polls to be postponed by a year, citing public health concerns because of the coronavirus pandemic.

While the NPCSC endorsed the postponement of the election in August, it did not make a specific ruling on the fate of the four back then.

However, since the extended Legco term started a month ago, pro-Beijing lawmakers have repeatedly called for action to be taken against the pan-democrats for filibustering with repeated quorum calls at council meetings.

Before Tam Yiu-chung, Hong Kong’s sole delegate to the NPCSC, travelled to Beijing on Monday, he also described filibustering as grounds for disqualification.

But as the resolution stopped short of mentioning delaying tactics, Lam argued that it was not aimed at stopping filibustering.

“We would not take away members’ qualifications because they deploy certain parliamentary tactics,” she said. “We would not like to see this … but that is not the purpose of this decision at all.”

Maria Tam Wai-chu, vice-chairwoman of the Basic Law Committee, which advises Beijing on Hong Kong’s mini-constitution, said the NPCSC’s decision could not be challenged in the city’s courts.

Tam Yiu-chung said the decision should serve as a reminder to lawmakers about being mindful of their conduct in the legislature.

Professor Johannes Chan Man-mun, a legal expert at the University of Hong Kong, criticised the resolution for bypassing the courts, saying it was unfair for the NPCSC to leave no room for lawmakers to explain or review their disqualifications.

Britain was quick to condemn Beijing’s move as “a further assault on Hong Kong’s high degree of autonomy”.

Foreign Secretary Dominic Raab said: “This campaign to harass, stifle and disqualify democratic opposition tarnishes China’s international reputation and undermines Hong Kong’s long-term stability.”