Malcom Turnbulls rookie Assistant Minister to the Treasurer Michael Sukkar is already fumbling badly, as he failed to rule out a massive $19 billion blow to the budget bottom line, further endangering Australias AAA credit rating.

When asked to rule out making mortgage interest payments tax deductable Mr Sukkar said: I will examine, and I know that the treasurer will look at, all good ideas.

The idea was immediately panned by housing economists, with the Grattan Institutes chief executive John Daley saying in media reports it would cost the budget $19 billion a year and do little to improve housing affordability, compared with tackling negative gearing and capital gains tax concessions.

Mr Sukkar says he doesnt want to announce ideas on day one in the job and yet has already ruled out looking at reforms to negative gearing reforms that outgoing NSW Premier Mike Baird and his Planning Minister Rob Stokes say are worthy of consideration.

The Coalitions plan to give big corporations a $50 billion tax cut is bad enough. Handing out billions in new mortgage tax breaks will put the AAA credit rating at risk and do nothing for housing affordability.

Only Labor has a sustainable plan to address housing affordability, a plan which has wide community and stakeholder support. Instead of considering poorly thought-out plans like mortgage interest tax deductions, the rookie Minister should address the elephant in the room, negative gearing.