Banks have been given a green light to hike rates on interest-only and investor loans as regulators scramble to manage a dangerously overheated property market in Sydney and Melbourne.

A raft of tough rules discouraging banks from those forms of risky lending was announced on Friday but was almost immediately slammed by property observers as too little, too late to curb insatiable investor demand. It is also almost certain to hit owner occupiers at a time of record-low wages growth and record debt.