The board is waiting for an opinion from the Department of Justice on the issue.

The government plans to auction the old Government Supplies Depot, but harbour activists say the planning brief that dictates the layout, height and plot ratio of the 1.6-hectare site was drawn up in the 1990s, years before harbour enhancement guidelines were created to curb rampant development on the harbourfront.

Mr Zimmerman's move comes after he filed a request to the board last year, calling for the site to be rezoned to increase the amount of open space and lower building density.

The board agreed with what he suggested, but ordered the Planning Department to review the planning brief.

Its members agreed with the principles the harbour group had suggested, such as more open space and stepped building heights to avoid a wall effect blocking views across the harbour. But they did not want to restrict the design and layout of a future development and believed there were other ways to achieve the same objectives.

Under the Town Planning Ordinance, the government has to prepare a new outline zoning plan when a site needs to be rezoned. This requires public consultation. A planning brief, however, is a guideline that helps property developers to prepare a master development plan for the board's approval.

Legal experts said the decision on the former government supplies depot would have an impact on other sites where rezoning applications were rejected on similar grounds.

Mr Zimmerman wrote to the board at the end of last month, demanding that it amend the Oil Street decision or face a judicial review.

'The board agreed the current zoning is not right,' said Mr Zimmerman, convenor of the pressure group Designing Hong Kong Harbour District.

'If it is wrong, it must be changed,' he said.

'They should proceed with the rezoning. Unfortunately it decided to confine the change to the planning brief, which is non-statutory. They are side-stepping the proper planning principle.

'The reasons for doing this is to leave the power of controlling the site with the government.'

He said the site had a special meaning for Hongkongers.

'Harbour protection is not just about reclamation, it is also about proper planning at the waterfront, reserving it for public enjoyment.'

In his letter, dated January 20, Mr Zimmerman said the grounds for the review would be that the board had made 'serious procedural and substantive errors' and 'failed to comply with the statutory duty imposed on it them'.

Eric Cheung Tat-ming, assistant law professor at the University of Hong Kong, said: 'If the development restrictions are made statutory, the room for deviation will be small. But if it is just an administrative statement, there will be more space for departure.'

Roger Ho Yao-sheng of the Mid-Levels Concern Group welcomed Mr Zimmerman's move. 'Our officials lack planning vision. They only care about how much the land can fetch at auctions,' he said.

The board said it ensured widespread public consultation before drawing up the planning brief.