Mr Justice Michael Hartmann granted an application by the Society for the Protection of the Harbour for a declaration that 10.7 hectares of temporary reclamation in and around Causeway Bay Typhoon Shelter is subject to the 1997 ordinance, which established a strong presumption against reclamation of the harbour.

The government is planning to reclaim temporarily 8.3 hectares of harbour near the promenade to build a road tunnel that will link the bypass to the Island Eastern Corridor, and to build a 2.4 hectare temporary breakwater 420 metres offshore.

But the society claims the plans will damage the harbour. Further, they say, it will fail to meet the requirements of the ordinance and a 2004 Court of Final Appeal ruling - that any reclamation must satisfy the test of 'overriding public need' and be supported by 'cogent and convincing materials'.

Adviser Winston Chu Ka-sun welcomed the judgment yesterday as a 'landmark ruling' and a victory for society and the public in the latest stage of its 14-year battle to protect the harbour from an 'open season' of government reclamation.

'The ruling shows that the harbour is still under legal protection, and the importance of the rule of law for Hong Kong,' he said.

The government must consult the public, he said, and show that there was an overriding public need for its plans, that reclamation would be kept to a minimum and there was no reasonable alternative.

Society director Hardy Lok Kung-chin said: 'We would like to see the temporary breakwater removed from the plans, and the government needs to go back and consider all the technical options for building the tunnel.'

In his judgment, Mr Justice Hartmann rejected the government's first argument, that the temporary reclamation was not affected by the ordinance. He declined to rule on its second argument - that, in any case, an overriding public need for the works had been demonstrated. He did not grant a request by government counsel Jat Sew-tong to refer in the ruling to the 'strong public interest in progressing with the project'.

A spokesman for the Transport and Planning Bureau said it would study the judgment and decide whether to appeal.

'We will implement the project in a lawful and reasonable manner as early as practicable.'

In the original plan, the completion date was 2016. Greg Wong Chak-yan, a geotechnical engineer and member of the Harbourfront Enhancement Committee, said the ruling would cause a delay to the bypass of one to four years.

Andrew Leung Yee-tak, chair professor in building and construction at City University, said the delay would be between two and four years.