New rules on critical infrastructure sales

All future sales of state-owned assets such as airports, ports, electricity networks and public transport will be subject to foreign investment rules.

The rules will be extended from assets sold to state-owned foreign enterprises, Treasurer Scott Morrison told reporters in Canberra on Friday.

He refused to say whether the recent Port of Darwin sale to a Chinese company would have been subject to the new rules.

"You don't look in the rear view mirror, you look through the windscreen and go forward," Mr Morrison said.

However he cited other examples including sales of the Melbourne and Fremantle ports and the NSW electricity network.

The proposed change would ensure future sales of critical infrastructure to privately-owned investors are scrutinised by the Foreign Investment Review Board.

Under existing rules the assessment of critical infrastructure was only required when assets were sold to state-owned enterprises.

The new measure takes effect from March 31 and will apply to investments of more than $250 million.

Mr Morrison denied the change would send a confusing message to Chinese investors that Australia was "not quite open for business".

"Every country in the world has their own set of arrangements and it's up to every country to set those arrangements," he said.