The NSW Planning Minister, Rob Stokes, has blamed negative gearing tax breaks for worsening housing affordability in Sydney, and declared the supply of new dwellings alone will not make property affordable for those who need it.

The comments undermine the federal government's refusal to consider changing property taxes to improve affordability, as well as its attack on the Labor opposition for its proposed cuts to negative gearing.

"Why should you get a tax deduction on the ownership of a multimillion dollar holiday home that does nothing to improve supply where it's needed?" Dr Stokes will say in a speech on Friday.

"We should promote investment in the type of housing that is needed by the burgeoning populations in cities like Sydney," his speech says.