Treasurer Joe Hockey has all but ruled out any changes to negative gearing by warning that altering the system could drive up rents and harm investors.

Earlier this week shadow treasurer Chris Bowen said Labor was open to tightening negative gearing concessions, which allow landlords to claim tax deductions for net losses on rental properties. Any changes would not affect existing landlords, Mr Bowen said.

"If you change negative gearing, then there are significant flow-on consequences for people that rent homes, and that needs to be properly considered," Mr Hockey said on Thursday.