Greens leader Christine Milne has moved to re-enter the political debate over the budget, seeking meetings with Labor and the Senate crossbench to a discuss alternative revenue measures in a potential circuit-breaker before Parliament's resumption next week.

Senator Milne says she is also ready to sit down with Treasurer Joe Hockey or any other minister to discuss budget compromise proposals, but she would not compromise on unfair proposals such as the $7 GP tax.

On Monday, Prime Minister Tony Abbott said the government would deal with the crossbench but what ''we're not prepared to do, though, is sell out the fundamentals''. He lashed the Labor and the Greens for ''saying no to everything''.

''What I say to all of the crossbench senators is if you don't like what the government is putting up, give us your alternative in terms of how we save money.

''And there were some alternatives that came up from one of the crossbench members of the federal Parliament, and frankly they didn't stack up for five minutes.''

Senator Milne wrote to Labor leader Bill Shorten, Palmer United Party leader Clive Palmer and all eight crossbench senators to outline her party's alternative proposals to raise revenue, including a levy on the big four banks, abolishing tax breaks for fossil fuels and higher taxes for millionaires.

In a softening of the Greens' at times doctrinaire approach to political strategy, Senator Milne said the Greens wanted to propose alternative measures to debunk the Prime Minister's assertions the opposition parties offered no alternatives to the Coalition's contentious budget measures.

''This is not an exclusive list, it's our list; they may have other things in mind,'' she said. ''They [the crossbench] will have had a bit of time now to think about things. They may have suggestions we can talk through.

''This will enable us, Labor, PUP and other independents to see if there is other common ground on raising revenue.''

Senator Milne said the proposed bank levy and a move to reduce tax avoidance by taxing discretionary trusts could win support. Asked if she would meet the Treasurer, with whom she hammered out a deal on the debt ceiling last year, she said ''Joe Hockey has got my number''.

Labor sources questioned Senator Milne's move to reposition her party, saying it had opposed the Coalition's proposed restarting indexation of the fuel excise and the temporary deficit levy, despite both being Greens' party policies.

Shadow treasurer Chris Bowen said that if the government put something to the ALP it would listen but ''our values and principles have been clearly outlined, our red lines. We are not prepared to negotiate … matters of principle like the universality of healthcare''.

On Tuesday, Mr Bowen rejected the idea of a tax on bank profits.

''Banks pay corporate tax and that's appropriate,'' he told reporters.

Mr Palmer, who met Mr Hockey's chief of staff on Monday, said his party still thought the GP co-payment and rise in fuel excise were unfair but held out the prospect of a possible deal.

He said his party was ''available to talk to anyone about anything''.

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