Prime Minister Tony Abbott says voters will eventually thank him for trying to repair the budget bottom line, even if it includes breaking his promise not to introduce new taxes.

But Mr Abbott says he knows people will be "disappointed" with some of his methods and is again refusing to rule out reports he will raise income taxes for those on higher wages.

Some Liberal MPs are leading a backlash against the deficit levy with some threatening to cross the floor in opposition to the move, if it is included in next Tuesday's budget, as expected.

They say it would breach the Coalition's pre-election pledge not to introduce new taxes.

But the Prime Minister says the Government's "most fundamental commitment of all" was to "get Labor's debt and deficit disaster under control".

And he says voters will eventually "thank" the Government if it meets its top promises.

"I'm not going to deny for a second that there will be people who are disappointed," Mr Abbott told Channel 9 this morning.

"No-one likes difficult decisions, Governments don't like taking difficult decisions, voters don't like the consequences of difficult decisions.

"But you've just got to make hard decisions at times like this, and I think in the long run the voters will thank us for doing what is absolutely necessary if Labor's debt and deficit disaster is to be tackled.

"I'm not going to comment on the detail of the budget, but I want to assure the people of Australia that this is a Government which is going to bring down a budget which is fair."

Opposition Leader Bill Shorten says no-one will be thanking the Government for breaking its promise of no new taxes.

"No political leader in the history of Australia has staked so much of their reputation on someone who keeps their election promises," he said.

"No-one has said so shamelessly, so brazenly, so quickly braking their promises. Tony Abbott, Australians should not thank you for breaking your promises."