An estimated $12 billion could be raised by the Government if the 2,000 non-departmental quarters were sold over the next three decades. But Deputy Secretary for Civil Service Mike Stone said yesterday the 50 sites might be more valuable if redeveloped. Mr Stone, who chaired a working group, said a plan would be formulated within the next few months to see how best such quarters could be disposed of in the next three to five years. He said it could take 30 years to get rid of all of them because tenants currently in them might remain in the civil service for another 20 to 30 years. Non-departmental quarters are government places not belonging to specific departments and are allocated for senior civil servants. Departmental quarters are for specific departments such as for the disciplinary forces. A programme would be drawn up to identify which sites should be disposed of first. 'We need to plan forward. Obviously, we need to give staff notice . . . Some of the sites are very popular. We don't want to unduly upset civil servants. 'In the short-term, we would invite agents to lease out flats to the private sector. We are also trying to sell individual flats because they are easier to sell,' he said. The number of leased non-departmental quarters has decreased from 3,135 in 1990 to 1,926 this month.