The government and Reserve Bank are taking aim at unsustainable house prices, with fresh attempts to cool the housing market. New moves to tighten mortgage lending include lowering the amount of lending to low-deposit borrowers, as well as consulting on debt to income ratios and how banks check whether their customers could pay off their mortgages if interest rates go up. It comes as the Reserve Bank warns a fall in prices would result in some recent buyers' mortgages exceeding the value of their house. The Property Investors' Federation chief executive Sharon Cullwick speaks to Māni Dunlop.