HONG KONG (AFP) -- A powerful new Hong Kong committee tasked with vetting politicians and officials for their loyalty disqualified an opposition lawmaker for the first time on Thursday, as authorities purge its institutions of anyone deemed disloyal to Beijing.

Cheng Chung-tai, one of just two opposition figures left in the city's legislature, was deemed disloyal on the basis of his previous statements and behaviour, chief secretary John Lee, who heads the vetting committee, told reporters.

"To those who pretend to... bear allegiance to the government, I will not be deceived by their flowery speeches and their attempts to sugarcoat," Lee said, adding Cheng had "lost his seat with immediate effect."

Lee did not detail what specifically Cheng had said or done that had led to his disqualification.

China is rapidly recasting Hong Kong in its own authoritarian image in the wake of huge democracy protests two years ago.

It has blanketed the business hub in a national security law that has criminalised much dissent and rolled out a campaign to ensure only so-called "patriots" can play a role in its politics.

That campaign has included a sweeping overhaul of the city's already limited elections, drastically reducing the number of directly elected seats and empowering a new committee to vet anyone for their political loyalty.

Only one non-government loyalist is now left in Hong Kong's partially elected legislature -- an independent who represents the city's medical sector.

Cheng, 37, was the only opposition lawmaker who did not resign in protest last year after four other legislators were disqualified.

In 2017 he was found guilty of "desecrating" the Chinese and Hong Kong flags by turning them upside down during a debate.

Thursday's decision illustrates how few opposition figures will be able to stand for office in the future.

New elections will be held for Hong Kong's legislature in December, but fewer than a quarter of seats will be directly elected and only those vetted for political loyalty will be allowed to stand.

The last time Hong Kongers were able to vote -- for district councillors in late 2019 -- pro-democracy candidates won a landslide.

Hong Kong's legislature now looks much closer to the mainland's, where laws are passed with near unanimous approval and no opposition is tolerated.

China committed to giving Hong Kong a degree of autonomy when it reverted from British colonial rule in 1997.

But it began moving quickly to dismantle the financial hub's democratic pillars in response to huge and sometimes violent democracy rallies that paralysed the city throughout 2019.