That's what compusory purchase orders are for. First off, the housing is to a greater or lesser extent required in urban centres to house proles to do the jobs proles do. Developers & large retailers have large "land banks" in urban areas, some of which have stood derelict for decades.
We need a "shit or get off the pot" law. If the land is not developed within, say 5 years, the owners get hit with punitive taxation on the value of the land. And not just the current market value, the vastly inflated book value.
That should loosen things up a tad
Chris
Again I totally agree (it must be the heat
But it doesn't get around the clear lack of political will. It's clear that it's lacking or it would be being dealt with as we speak - and not just allowing folk to build loft extensions without planning permission.
I also firmly believe that before a single new house is built there should be a survey of all vacant domestic properties. These should be made habitable and people be allowed to rent or own them. Mirroring your point above the owners of said properties should prepare them for habitation or sell them to someone who will.