''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.