Prime Minister Tony Abbott and Finance Minister Mathias Cormann have emerged from a key Cabinet meeting, all but confirming next week's budget will include a debt tax.

Cabinet yesterday considered imposing higher taxes on workers in the top income brackets to share the burden of paying back the nation's debt.

Liberal figures, including former treasurer Peter Costello, and current backbenchers have joined business groups in criticising the idea of raising taxes for high income earners.

Senator Cormann says the Government will deliver the "lowest possible taxes" given the dire budget situation.

"There is a need for an immediate special effort, in order to put ourselves in a stronger starting position as we repair the budget," he said.

"And that special effort needs to be spread fairly and equitably and the only way you can ensure you do that is by also considering appropriately targeted measures in the tax system."

People in the top income tax bracket of $180,000 and above are in the Government's sights and the next bracket down, which kicks in at $80,000, may also be hit.

"What we would ask people across Australia to do is to trust us," Senator Cormann said.

Mr Abbott denied accusations from his Liberal MPs, including Queenslander Teresa Gambaro, that the new tax would be a broken election promise.

"I'm going to be able to look people in it eye on Tuesday night and on Wednesday morning and beyond and say we are all in this together, we are all doing our bit," he said.

He says the budget will keep the Coalition's commitments and be "fair".

"We will honour the commitment we gave to the Australian people pre-election to get the budget back under control, but we will do it in ways that are fair," he said.

The Coalition's policy document from last year's election states: "We pledge to the families of Australia that we will never make your lives harder by imposing needless new taxes".

It also highlights a quote from Mr Abbott, who said in March 2012 that "no country has ever taxed itself into prosperity".

Treasurer Joe Hockey will hand down the budget on Tuesday.