London property scandal finally dawns on PM

There has been a release to UK media of a speech by David Cameron on his Far East tour. Private Eye and the Independent of the media I habitually read have reported for some time on the scandal of anonymous companies owning swathes of London property. Others, including the Guardian, clearly have done so also. It comments on the Cameron speech:

In March, Transparency International concluded that shell companies are a common way for moving corrupt money around the world, hiding funds that were intended to be invested locally. It added: “The corrupt are helped to buy properties by lawyers, accountants and estate agents who do not ask where the money is coming from – which by law in most countries, including the UK, they are supposed to do.”

The question is: why has no action been taken by the Chancellor and DCLG to expose the end-owners of this real estate, and why has this conduit for dirty money, which must add to the overheating of the metropolitan economy, not been raised as an issue at prime minister's questions?