The party was founded in 2006 and was once considered the radical faction in Hong Kong's pro-democracy camp. It was known for its boisterous street-level campaigning, often spearheaded by the now-jailed activist "Long Hair" Leung Kwok-hung.

However, its decline was hastened after Beijing imposed a national security law in Hong Kong in 2020 in the wake of massive and sometimes violent pro-democracy protests the year before.

"Next year marks the 20th anniversary of the League of Social Democrats. However, we will not survive to see that day and will announce our disbandment," the LSD said in a message to reporters, adding that more details would be announced Sunday.

The LSD consistently called for greater democracy in Hong Kong and advocated for grassroots causes, criticising social and economic inequalities in a city with one of the world's largest wealth gaps.

"When the system cannot faithfully represent the people's demands and becomes a tool for the ruling classes, we must rely on a movement of the masses outside the system to put pressure on those in power," LSD wrote on its website.

The party held three seats in Hong Kong's legislature at its height.

It seized the spotlight in 2008 when then-party leader Raymond Wong threw bananas at Hong Kong's leader during his annual policy speech, protesting against welfare cuts.

The party's firebrand image diminished in the late 2010s, however, when younger, more radical parties emerged to contest China's rule.

Then came the 2020 national security law, which China and Hong Kong argue was needed to curb political unrest but critics say has been used to quell dissent and erode rights.

- Subversion case -

LSD figurehead and former legislator Leung was arrested in 2021 and jailed last year as part of a sprawling subversion case involving 47 opposition figures.

The party has held small public protests in recent years, often under heavy police surveillance.

Four members, including current leader Chan Po-ying, were fined this month for raising money in street campaigns "without permits".

Dickson Chau, an LSD vice-chairperson, told the court during their trial the activists hoped to promote social progress but "unfortunately, the government's response is prosecution".

LSD activists are among the handful of remaining Hong Kongers who still publicly mark the anniversary of the 1989 Tiananmen Square crackdown after such commemorations were banned by the government.

Scores of civil society groups have closed since the national security law came into effect, with hundreds of activists arrested, jailed or in exile.

Hong Kong's legislature is now opposition-free after authorities revamped electoral rules in 2021 so only "patriots" could hold office.

The Democratic Party announced this year that it had begun a formal shutdown process. The Civic Party closed its doors in 2023.

Regina Ip, convenor of the Hong Kong government's cabinet, told AFP the opposition parties "have done great damage to Hong Kong and to the proper functioning of (the Legislative Council)" in a Wednesday interview.

"It is a good thing that they should wind down," Ip added.

Human Rights Watch's Maya Wang said the LSD's disbandment showed how fast and furious Beijing's repression in Hong Kong had been.

"Its members have fought vocally for democracy for years and persisted in doing so despite escalating harassment and harsh imprisonment after the National Security Law," Wang said in an email to AFP.

"One can only imagine the kind of additional threats the group must be facing from Beijing before they decided to close shop."