There is a last gasp plea from the commercial property industry ahead of today's speech from Prime Minister John Key to mark the opening of Parliament.

As part of a revamp of the tax system, Mr Key is expected to target the tax breaks landlords currently enjoy.

Property Council president Chris Gudgeon says proposals to change depreciation rates and applying land taxes, are equivalent to raising taxes from 30 percent to 32 percent.

"If government want to do something about the residential sector, please, at the same time be careful not to clobber the productive sector, New Zealand businesses, because that's not what should happen.

"We just want to be sure that they implement things very carefully and don't hit the productive sector, don't hit businesses and don't hit people who are saving and investing in the New Zealand share market and Kiwisaver schemes."

Mr Gudgeon says more that 80 percent of commercial property is owned directly by businesses and an ill-considered application of tax changes will have the effect of increasing the cost of doing business in New Zealand.

In addition to overhauling property tax, Mr Key has recently not ruled out the tax working group's recommendation to increase GST from 12.5 percent to 15 percent. He has also indicated that tax avoidance measures which allow wealthier people to dodge paying tax will be targeted.