A green group has warned that approval of a proposal to make it easier for developers to acquire old buildings will open a Pandora's box. Green Sense called for the plan to be delayed until town planning measures had been reviewed to plug loopholes that could be abused to develop tall and bulky buildings in old districts. The group estimates there could be as many as 735 high-rise and bulky blocks in old areas in 10 years, creating a wall effect, if the proposed changes get the go-ahead. The proposed amendment to land resumption laws would allow a developer to force homeowners to surrender their flats if it acquires 80 per cent of the properties, compared to the present 90 per cent threshold. The change will apply to three types of buildings - those with all properties but one acquired, buildings older than 50 years, and industrial buildings more than 30 years old not in an industrial zone. Such groups as the Institute of Surveyors, Construction Association and Real Estate Developers Association support the idea. Green Sense president Roy Tam Hoi-pong warned: 'It would give unrestricted power to developers to build tall and bulky buildings, unless we have comprehensive town planning measures in place.' The government is reviewing the practice of granting developers extra floor space for so-called green features such as balconies and utility platforms. Critics say they abuse this to build taller and bulkier buildings. A separate review is being conducted of planning guidelines to reduce the number of parking spaces at private residential estates, often built directly under the residential blocks and also blamed for tall and bulky buildings. Tam estimated there would be about 7,350 blocks older than 50 years by 2019.