Tax on non-primary properties solves this if you can get it past vested interests.

Reasonable tax breaks for your primary or only home, and none for second homes / investments you let out.

That gives a valve to perform qualitative easing on the housing market whenever you need to, and is not uncommon in other parts of the world.

EDIT: Having read the responses below I’ve realised I didn’t clearly word what I meant here, that’s my bad. I mean a holding taxation rather than CGT. Essentially, an elevated annual property tax on non-primary properties that would have the effect of penalising investors relative to those seeking a home to live in.