The government and unions criticised the Coalition's draft tax and jobs plan for northern Australia, which includes tax incentives to attract private sector workers to cities such as Darwin, Cairns and Karratha.

The leaked plan, Vision 2030, proposes to redirect foreign aid into a mega-project in northern Australia and says an Abbott government proposes in its first term to ''relocate substantial and relevant components of federal departments and commonwealth agencies, such as CSIRO, to key urban areas in northern Australia''.

Public Service Minister Gary Gray said the opposition's ''simplistic thought bubble'' would have dire consequences.

''The leaked Coalition document reveals the Liberals' secret and expensive plan to force Australians to move north of the Tropic of Capricorn and to slug families in our major cities to pay for it,'' he said.

Mr Abbott was forced to back away from elements of the plan that he said had been put out for consultation.

He ruled out splitting Australia into different tax zones while pointing out some zonal rebates had been in place for many years.

''I certainly haven't ruled out careful, fiscally responsible incentives,'' he said during a campaign stop in Queanbeyan on Thursday.

''We will be telling you exactly what our specific proposals are in good time before the next election.

''It's not a bad thing to have Commonwealth facilities in different parts of Australia … but we certainly have no plans, and it would be unconstitutional, to civilly conscript public servants.''

He said northern Australia should have access to skilled migrants from overseas to fill labour shortages.

Trade Minister Craig Emerson said the northern Australia plan was a ''wacko'' idea, and its leaking to the media showed some Coalition MPs agreed.

''You put one part in to this so-called policy, one part in from Gina Rinehart, one part in from Joh Bjelke-Petersen, one part in from Tony Abbott, stir it around and what have you got? Troppo Tony,'' he said.

Member for Canberra Gai Brodtmann said she was worried about Canberra families facing the prospect of being sent thousands of kilometres north.

''The place of federal government is Canberra, not Karratha or Cairns,'' she said.

Community and Public Sector Community Union national secretary Nadine Flood said most Australians would support sensible, properly planned moves to boost regional employment in the north but the Coalition's plan failed the credibility test.

''Forcing tens of thousands of public servants to move thousands of kilometres to work in small developing towns like Karratha is an astonishing idea from an opposition obsessed with 'wasteful' government spending,'' she said.

''Tony Abbott is using the public service as a political football again. One day he wants to slash jobs and put families out of work, the next day he wants them to move to northern Australia.''