Hong Kong could keep its freedoms and autonomy beyond the 50-year deadline set by Britain during the 1997 handover, the city’s leader has suggested, if its citizens show loyalty to Beijing.

In what appeared to be a novel carrot-and-stick approach to appealing for calm, chief executive Carrie Lam said there would be no need for change in 2047 if the current system was running “smoothly”.

Hong Kong, which enjoys freedoms and independent institutions not seen on the mainland, has been embroiled in major protests since June last year amid a public perception that Beijing is rolling back civil liberties.

Part of the deal which saw the city handed back to China from the UK was a promise that Hong Kong would be allowed to maintain its own capitalist economy and other vestiges of Western rule for at least 50 years, under the “one country, two systems” principle.

Communist Party leaders are not opposed to extending the arrangement, however, with Hong Kong’s unique position enabling it to flourish as an international financial powerhouse - and thereby contributing significantly to Beijing’s coffers.

Speaking in her first appearance this year at the city’s assembly - the Legislative Council - Ms Lam told local MPs that “temporary misunderstandings” should not be allowed to derail Hong Kong’s long-term prospects.

"Only if we insist on implementing the 'one country, two systems' principle and practise it continuously and fully ... then I think there will be enough grounds for 'one country, two systems' to move ahead smoothly and there would be no change after 2047," Ms Lam said.

"We have to uphold the principle of 'One country.' Only by doing this, can 'one country, two systems' be moving forward smoothly.”

The chief executive urged the city's youth, who have been at the forefront of the at-times violent protests, to not violate the principle. "The scenario they worry about today may be triggered by their own hand," Ms Lam said.

The pro-democracy protests were sparked by proposed legislation that could have seen suspects extradited to face unfair trials and possible torture in China.

They now enjoy the support of 59 per cent of all city residents, and almost nine in 10 of those aged 18-20, according to a survey conducted for Reuters by the Hong Kong Public Opinion Research Institute in December.

While Beijing has sought to frame the protests as a violent separatist movement, only 17 per cent of respondents expressed support for seeking independence from China.

Ms Lam said Thursday she hoped next month to announce the formation of a committee to look into the root causes of the unrest. Academics, experts and social leaders have been recruited to the Independent Review Committee, although some are reportedly reluctant to join out of fear of personal attacks or online harassment by opponents leaking personal information.

During a contentious session, Ms Lam repeatedly defended police action as angry opposition politicians demanded to know why her government isn't responding to public demand for an independent investigation into alleged police brutality.

She said that police were merely performing their duty to maintain public order and had deployed "minimal force." The government says complaints against police are being handled by the force's own investigative division.

At one point, a politician asked Lam, a practicing Catholic, whether she was afraid of going to hell. When she dodged the question in her reply, he asked her "When are you going to die?"

Several opposition MPs were ordered to leave the meeting after repeatedly interrupting Ms Lam.