Hong Kong's top court has declared it unconstitutional to deny social security to new immigrants.
The unanimous Court of Final Appeal ruling means new arrivals will no longer be required to live in the city for at least seven years before they can apply for Comprehensive Social Security Assistance (CSSA) benefits.
Ho Hei-wah, director of the Society for Community Organisation, said the ruling may lead to an annual increase of 5,000 to 7,000 applications from new immigrants.
It could add HK$750 million annually - an increase of 3.5 per cent - to the CSSA bill.
Secretary for Justice Rimsky Yuen Kwok-keung ruled out any suggestion the government would ask Beijing for an interpretation of the Basic Law.
"Rest assured, we will not be taking any unnecessary steps in this regard," Yuen said. "We will respect the judgment, so don't worry."
Matthew Cheung Kin-chung, the secretary for labour and welfare, said the government would now reinstate a one-year residency requirement.
Chief Executive Leung Chun-ying said government departments had already started assessing the ruling's impact on the CSSA system and other policies.
Chief Justice Geoffrey Ma Tao-li, Mr Justice Roberto Ribeiro, Mr Justice Robert Tang Ching, Mr Justice Kemal Bokhary and Lord Justice Phillips handed down the judgment and unanimously allowed the appeal launched by new immigrant Kong Yunming.
The top court ruled that the seven-year residency rule breached Article 36 of the Basic Law, which says every citizen has a right to social welfare benefits under the CSSA scheme.
The policy conflicted with the one-way permit policy designed to promote family reunions in Hong Kong and the population policy aimed at rejuvenating the ageing population, the court said.
The government's explanation that the seven-year policy was intended to save money and ensure the sustainability of the social security system was not reasonable, the court stated.
Kong, 64, who started the judicial review process in 2008 when she was a homeless new immigrant, said: "It's not exactly joy. But it's more like closure for me … and hope."
Kong's appeal was dismissed twice before it was brought to the Court of Final Appeal last month.
Ho, whose SoCo organisation has supported Kong, said the ruling was a "win for the whole of Hong Kong" on welfare rights.
He added that the financial burden on the government would not be large.
"It must be known that apart from the residency requirement, there are many other requirements for CSSA," said Ho.
He said single-parent families with mothers waiting to fulfil the residency requirement would gain the most benefits.
The government has spent HK$19.7 billion on CSSA in the past year. Last month there were 261,289 CSSA cases, 9,573 involving new immigrant family members.
The seven-year residency requirement targeting new mainland immigrants was implemented in 2004.
Additional reporting by Jeffie Lam