Cameron believes implicitly and blindly in the private sector. He deludes himself that getting the private sector to pay for improving these estates by allowing them to build houses for sale as well will somehow magically increase the number of homes in the social sector.
To be fair to him, outside the major conurbations, which is where all the sink estates are, this policy of insisting that 40 percent of all homes on a new development must be social housing has done much to provide both more homes and more social sector homes.
My village has acquired nearly 100 social sector homes this way plus much more socially mixed developments with everything from small flats and houses to large detached houses on the same site, which is typical of the distribution of village housing anyway.
In conurbations where the sites concerned already containing social housing and rebuilding in the private sector will encroach on the number of social homes provided and where any market housing, no matter how small will command a price way beyond the means of local people, even with the right to buy then this kind of development is completely unacceptable.