HONG KONG (REUTERS) - Support for year-long pro-democracy protests in Hong Kong has slipped, now getting the backing of only a slim majority, as the city braces for the imposition of Beijing-drafted national security legislation, a survey conducted for Reuters showed.

Protests escalated last June over a since-withdrawn Bill that would have allowed extraditions of defendants to mainland China. They later morphed into a push for greater democracy, often involving violent clashes with the police.

The protests have resumed, but with far fewer participants, since China announced plans for the security law, which has alarmed foreign governments and democracy activists in Hong Kong.

The survey conducted by the Hong Kong Public Opinion Research Institute between June 15 and 18 showed the legislation is opposed by a majority in the financial centre.

But the poll also showed support for protests dropping to 51 per cent from 58 per cent in a previous poll conducted for Reuters in March, while opposition to them rose to 34 per cent from 28 per cent.

"It may be psychological, because Hong Kong people see Beijing is getting more hardline," said Prof Ming Sing, associate professor of social sciences at Hong Kong University of Science and Technology.

"If you keep insisting (on the demands), it's impractical."

Events on the ground also point to a loss in momentum, with most demonstrations in recent weeks attended only by hundreds and ending quickly. Police, citing coronavirus restrictions, have not given permission for rallies recently and have arrested large numbers of those who turned up anyway.

Pro-democracy labour unions and a student group last week failed to garner enough support to hold strikes against the proposed security legislation.

The shift in backing for the protests has occurred mainly at the extremes, with those who strongly support them dropping to 34 per cent from 40 per cent, and those who strongly oppose them rising to 28 per cent from 21 per cent. The number of those who "somewhat" support or oppose the protests remained stable.

The particular demands of the movement have also seen a drop in support. The request for an independent commission of inquiry to look into how police handled the demonstrations saw a 10 percentage point drop from March to 66 per cent.

Universal suffrage, another key demand, was backed by 61 per cent, down from 68 per cent. The resignation of Hong Kong leader Carrie Lam was supported by 57 per cent versus 63 per cent three months ago.

Opposition to the demands rose to 21 per cent from 15 per cent.

Prof Samson Yuen, assistant professor in the political science department at Lingnan University, said support for the protesters' demands was "still high" but could have dropped because the security law has overtaken the protests as the main topic in the public discourse.

"Who would still talk about (protest) demands when the national security law is coming?" he said.

Mrs Lam's office and China's Hong Kong and Macau Affairs Office, which comes under the State Council, or Cabinet, did not respond to requests for comment.

For the poll, which had a margin of error of plus or minus 3.2 percentage points, 1,002 respondents were randomly surveyed by telephone. The results were weighted according to the latest population figures.

The poll was conducted when Beijing's intention to introduce legislation against terrorism, subversion, separatism and foreign interference was known but few details were available.

While the draft of the new law is yet to be finalised, key features of the legislation have since been released, revealing that Communist Party central authorities will have overarching powers over its enforcement, including final interpretation rights.

The poll showed 49 per cent of respondents strongly opposed Beijing's move, with 7 per cent "somewhat" opposing it. Support for the legislation added up to 34 per cent, with the rest indifferent or undecided.

"I object to the law because the (Beijing) government is interfering in Hong Kong's business," said engineer Charles Lo, 29, who participated in the survey. "It will also suppress our freedom of speech and hinder the democracy movement."

The law has stoked fears that Beijing is further eroding extensive autonomy promised to the territory when Britain handed it back to China under a "one country, two systems" formula in 1997.

Hong Kong and Beijing authorities have repeatedly said the legislation would target only a small number of "troublemakers", while rights and freedoms would be preserved. They say it will bring stability to a city rattled by the protests.

"Before June last year, I didn't think Hong Kong needed national security laws because we were so peaceful and safe, but now I think it's necessary," said another survey respondent, Hui, a retiree in her 50s.

The poll also showed that support for the idea of Hong Kong independence, which is anathema to Beijing and is expected to be a focal point in the looming legislation, remained relatively unchanged at 21 per cent. Opposition to the idea grew to 60 per cent from 56 per cent.

Compared to the previous poll, fewer respondents primarily blamed the local government - 39 per cent v 43 per cent - or the police - 7 per cent v 10 per cent - for the current state of affairs in Hong Kong, while more blamed the pro-democracy camp - 18 per cent v 14 per cent - and the central government in Beijing - also 18 per cent v 14 per cent.

Another finding was a rise in support for local, pro-Beijing politicians ahead of the Sept 6 election for the Legislative Council, known as LegCo.

Pro-Beijing candidates were supported by 29 per cent of respondents, up from 22 per cent. Support for pro-democracy politicians remained strong at 53 per cent, but dropped five points.

A split in lower level district elections in November resulted in the pro-democracy camp winning over 80 per cent of the seats.