The Commonwealth Bank is freezing new lending to property investors looking to switch banks and refinance their mortgage, a move designed to slow strong growth in its lending to landlords.

The country's biggest bank on Wednesday cited "regulatory commitments" as one factor when explaining the decision, which follows a recent patch of fast growth in lending to housing investors.

Commonwealth Bank has been expanding quickly in the housing investor market, where bank growth is capped at 10 per cent per year. Credit:Glenn Hunt

Banks have a 10 per cent speed limit on how quickly they can expand in the property investor mortgage market, under a policy introduced by the Australian Prudential Regulation Authority (APRA) in late 2014 in response to risks in the mortgage market.

This rule has caused banks to regularly change their lending policies for investors, who economists believe have driven much of the rapid price growth in Sydney and Melbourne in recent years.