The green groups say no buildings should be erected on the 80-hectare site, half of which is within the Deep Bay Area, listed as a wetland of international importance in 1995.

Albert Lai Kwong-tak, director of the Conservancy Association and Civic Party vice-chairman, said the developer had adopted a 'ridiculous strategy' to meet a 'no-net-loss' principle.

This non-binding principle, laid down by the Town Planning Board in 1997, states that any development in the Deep Bay Area should ensure there is no decline in the wetland functions of the fish ponds, which provide food and roosting grounds for birds. 'The developer has abandoned the fish ponds in the past few years after acquiring them,' Lai said.

'Lack of care has lowered the ecological function of the fish ponds. If you now ask town planners to let you develop the land because your project will enhance the fish ponds' value, I think this is no different from the 'destroy first, develop later' approach.'

The plan for the Fung Lok Wai project involves 19 blocks of flats 15 to 19 storeys high, on 5 per cent of the site area. The remaining area would be be preserved and managed by the developer.

Roy Tam Hoi-pong, president of Green Sense, criticised the developer's proposal to combine fish ponds to form larger ones. 'This is just another trick to achieve no net loss. By removing the embankments that separate the ponds, the water surface is enlarged,' Tam said.

Cheng Nok-ming, conservation officer of the Bird Watching Society, said getting rid of the embankments would affect some birds who need to stand on the side of ponds to get food.

'Also, the 19 residential towers will be like giants to those birds that like flying around, and they will no longer come,' Cheng said, naming the greater spotted eagle and the imperial eagle, two vulnerable species according to the International Union for Conservation of Nature.

Lai, Tam and Cheng called for the government to swap land with the developer to relocate the project.

The Town Planning Board is the remaining hurdle for the project, which secured a work permit from the Environmental Protection Department in 2009. The board is accepting public comments on the proposal until September 23.

Yau Wing-kwong, a board member, said he could not comment until he received the latest paper about the project, but hoped the developer would keep its original plan to hand over the long-term management of the wetland to WWF Hong Kong.

Cheung Kong could not be reached for comment yesterday.