The move follows a review triggered by the 2006 row over extra floor space granted to Henderson Land Development for its Grand Promenade project in Sai Wan Ho.

Henderson was able to almost double the floor area of the project under a policy that exempts space used for building green features, basic and recreational facilities from the gross floor area.

The policy also awards developers extra floor area if they dedicate the space for public use.

'A poll conducted by the Buildings Department last year shows that most people still want green features in buildings,' a Development Bureau official said yesterday. 'But excessive facilities might have an impact on the surrounding neighbourhood. We will ask the public to strike the balance.'

A departmental review of 97 residential and commercial developments approved in recent years showed that in some low-rise projects developers had been able to more than double the floor space by building car parks.

Exemptions ranging from 3 to 33 per cent were granted for basic facilities such as plant rooms and 3 to 29 per cent for building such green features as balconies and sky gardens.

Under the new proposals, the total exempted floor area would be capped at 25 to 35 per cent of total floor area for residential developments and 20 to 30 per cent for commercial developments.

The cap will not apply to bonus floor area and parking space. But a Development Bureau spokesman said the government did not usually give away bonus floor area and the amount would be minimal.

Developers that enjoy gross floor area concessions would be required to comply with environmental requirements - for example providing 20 to 30 per cent of green area within the development.

Developments on narrow sites would have to be set back not less than 7.5 metres from the street.

Basic facilities required by law, such as rubbish storage rooms, fire refuge areas, and telecommunications and broadcasting equipment rooms would no longer be exempted. The bureau also suggests reducing the number of exempted parking spaces for developments, especially those at easily accessible locations.

'Existing planning guidelines asked each development to build a minimum amount of parking space, which eventually allows low-rise developments to double their gross floor areas,' a Development Bureau official said.

Other measures include reviewing the definition of green features and defining more clearly the discretionary power of the Building Authority in allowing exemptions.

Developers who dedicate areas for public passage or road widening would also receive less bonus floor area than at present.

A Development Bureau spokesman said the Sustainable Development Council would hold a three-month public consultation early next year on the topic. He insisted the proposals would not hurt the property market.