Assistant Treasurer Kelly O'Dwyer is insisting all tax reform options remain "on the table" but is playing down the prospect of the Turnbull government curbing negative gearing.

Negative gearing is the practice where investors use losses made on property investments to reduce their overall taxable income. Some 1.3 million Australians use the concession, making it a politically sensitive area for reform.

Former Treasurer Joe Hockey told Parliament this week that negative gearing should restricted.

"Negative gearing should be skewed towards new housing so that there is an incentive to add to the housing stock rather than an incentive to speculate on existing property," Mr Hockey said in his valedictory speech.