But their pro-establishment rivals defended the government’s move, labelling Cheng an exception and argued officials remained committed to keeping Legco diverse.

“The Candidate Eligibility Review Committee will not allow anyone who pretends to uphold the Basic Law or pretends to bear allegiance to the city to enter the system,” Lee said.

The lawmaker responded by saying that he considered himself a patriot but would respect the committee’s decision.

In announcing the vetting committee’s decision, Lee said: “Scammers are skilled in playing different roles. But for these people who pretend to bear allegiance, I will not be tricked by their words as they try to cleanse themselves.”

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Following Beijing’s revamp of the political system, government officials and pro-Beijing figures have promised the legislature would remain diverse, which in turn has put the spotlight on the Democratic Party.

“I think the decision to disqualify Cheng Chung-tai was at best inconsistent with and incoherent to the government’s apparent push for the Democratic Party to take part in the Legislative Council elections in December,” said veteran pan-democrat Alan Leong Kah-kit, who is the chairman of the opposition’s Civic Party.

Leong pointed to an opinion piece published on Monday by pro-Beijing veteran Lo Man-tuen in which he warned the Democrats against boycotting the elections, calling it a “dead-end rally”.

“This is a typical case of ‘the left hand doesn’t know what the right hand is doing’,” Leong said.

Democratic Party chairman Lo Kin-hei said the disqualification was yet another indication of how tense the political landscape remained but he doubted it carried any meaning beyond that.

“I don’t think it constitutes any signal,” he said.

Cheng’s situation was vastly different from what the Democrats faced, and so the vetting committee’s decision shed little light on whether party members would indeed be allowed to run in the future, Lo said. He had earlier explained that taking part in the elections would be left up to the individual.

According to a source familiar with the party’s thinking, its assessment was that Beijing could view the participation of the 26-year-old organisation in the political process as more valuable than the role of a single lawmaker.

“We have a longer history, broader base of supporters and the optics of being seen as having a democratic camp by people outside of Hong Kong,” the insider said.

But pressure was mounting on the party to decide how to respond to the warnings by officials and pro-establishment figures that members should take part in elections or risk facing consequences, he said.

Pro-establishment lawmaker Paul Tse Wai-chun argued the disqualification did not contradict the pledge by authorities that the legislature would be diverse. Tse also disagreed with the suggestion that Cheng had tempered his localist beliefs, insisting instead that he changed his views according to the direction of political winds.

“While we may need a legislature that is not lopsided, we don’t need a chameleon. There are people out there who have ‘light yellow views’ who can take his place,” said Tse, referring to the colour associated with the opposition camp.

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Lau Siu-kai, from the semi-official Chinese Association of Hong Kong and Macau Studies, said the promise of ensuring Legco remained diverse did not mean Beijing would lower its standards for lawmakers.

He noted that Cheng had desecrated the national flag and backed localist causes. Despite becoming less confrontational in recent months, “he had never openly renounced his political stance in the past”, Lau said.

Rather the decision to unseat him and deny him a role on the Election Committee showed how important the body was in the eyes of Beijing, he added. Lau dismissed the notion that the disqualification was in any way tied to the lawmaker’s failure to attend a seminar that senior Beijing official Huang Liuquan delivered at Legco on Monday.

During the event, the deputy director of the State Council’s Hong Kong and Macau Affairs Office briefed lawmakers about China’s latest five-year national development plan, which prioritises domestic markets, and urged them to make up for the “wasted time” after the anti-government protests.

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Former Democratic Party members Tik Chi-yuen and Francis Chau Yin-ming, seen as moderates Beijing is willing to accept, were confirmed as candidates for the Election Committee polls.

Tik said even if he got through this time, there was no guarantee his actions would not be deemed inappropriate in the future.

He said his camp was still more inclined to criticise the government than their pro-establishment rivals. “It’s good if the government can meet us to discuss how far we can go in [opposing authorities],” he said.

Last November, the opposition camp resigned all together in protest over the disqualification of four colleagues after Beijing adopted a resolution on candidacy, but Cheng and Pierre Chan, an independent, decided to remain.

At the time, a spokesman for the State Council’s Hong Kong and Macau Affairs Office condemned the mass resignation but praised “an opposition lawmaker” for being wise to stay on.

Cheng was a key member of Civic Passion, formed in 2012 and known for its stance against mainland China and the Communist Party. He became chairman in 2016 and was elected as a lawmaker for the New Territories West geographical constituency.

Additional reporting by Tony Cheung