About 84 per cent expressed worries about air quality as more tall buildings went up, blocking wind and sunlight.

Nearly 90 per cent urged the government to consider environmental impact when granting approval to developers to build high-rises in redevelopment projects.

About 34 per cent said they would consider leaving Tsuen Wan because of the poor air quality.

Green Sense chairman Roy Tam Hoi-pong said: 'Aged buildings in old areas of Tsuen Wan are only four to six storeys high, but they are being surrounded by high-rises. Residents living in these old buildings suffer from poor air quality as tall curtains are created around their living environment.'

The group pointed to a project in Yeung Uk Road in which two tower blocks - each more than 40 storeys high - were being built. Mr Tam said the buildings would block ventilation and light in nearby Chuen Lung Street. 'The residents nearby are greatly upset by the planning,' he said. 'The government and private developers should not carry out these projects at the expense of residents' health and quality of life.'

Mr Tam said other districts such as Sham Shui Po, Tai Kok Tsui, Mong Kok, Hung Hom and Kwun Tong were also hit by bad planning.

'We studied 36 projects by the authority which are either completed or still in progress and we found all of the projects involved construction of high-rises which form a wall that blocks wind and worsens air quality,' he said.

The authority said that since its inception in 2001 it had awarded joint-venture contracts for 11 projects. All had complied with all standards and guidelines.

The chief executive of the Tsuen Wan Development and Promotion Association, Benjamin Chan Han-pan, said the group had collected 3,000 signatures seeking better planning.

'We will continue to gather signatures from residents till March and then we will submit them to the planning bureau to express our concern and urge the government to make better use of our open space and build more recreational facilities for us,' he said.