The Green Party says it has no confidence that the new Productivity Commission will take a proper look at housing affordability.
The Government has announced that the commission's first inquiry will be into house prices.
Both the Greens and the National Distribution Union believe it's another opportunity to consider a capital gains tax but accuse the commission of being ideologically driven.
Greens co-leader Russel Norman says the inquiry should look at introducing a capital gains tax on property apart from the family home - an idea supported by the union's general secretary, Robert Reid.
Both believe, however, that the presence of former ACT candidate Graham Scott on the commission makes serious consideration of the matter unlikely.
Commission chair Murray Sherwin says it will consult widely. The intention, he says, is that its inquiries be substantive and driven off a very strong evidence base.
When the commission formally begins work on Friday, Mr Sherwin will be joined by fellow commissioners Sally Davenport and Dr Scott.