Greens Leader Christine Milne.

Greens leader Christine Milne.

Greens leader Christine Milne "could not be happier" about helping to block Kevin Rudd's first emissions trading scheme four years ago - even though the carbon package she later negotiated faces the prospect of being axed by an incoming Tony Abbott-led government.

Senator Milne's declaration that she has no regrets comes amid uncertainty over the future of the carbon price agreed between Julia Gillard, the Greens and crossbench MPs following the 2010 election.

Mr Abbott insists he will have a mandate to axe the carbon tax if the Coalition wins this Saturday's election, as expected, and has threatened to send voters back for a double-dissolution election should Labor and the Greens later block his repeal bill in the Senate.

Senator Milne used an appearance at the National Press Club on Wednesday to appeal to voters to support the Greens in the Senate. This would ensure Mr Abbott did not gain a blank cheque in the upper house to walk away from climate action.

But with the future of Ms Gillard's carbon pricing scheme now in doubt, Senator Milne said she had no regrets over the Greens' actions in rejecting Mr Rudd's Carbon Pollution Reduction Scheme in 2009 when public support for action was greater.

Mr Rudd's original emissions trading scheme was rejected by the Senate twice in 2009, with the Greens arguing it did not go far enough and siding with the Coalition. Two Liberals crossed the floor and voted with Labor in the Senate in December 2009 - meaning the scheme could have narrowly passed if the Greens were on board.

Mr Rudd subsequently deferred his climate plans, a decision which helped lead to his dumping as party leader in 2010.

Senator Milne said she "could not be happier" with the decision to back effective action on climate rather than the first Rudd government scheme.

"If we had had the CPRS in place now, the carbon price would be less than $1, there would be no mechanism for increasing the target and we would be stuck with a completely ineffectual scheme, whereas what we have got now is an 8 per cent reduction in emissions and a transformation going on around the country," she said.

Regardless of the outcome of Saturday's election, Labor and the Greens will still control the Senate until at least June next year.

Senator Milne acknowledged a Labor opposition may allow the axing of the carbon price to pass the Senate, but refused to concede the original CPRS would be better than nothing at all.

"We need the Greens there [in the Senate] in force to keep Labor honest and keep them on track because, frankly, in opposition who knows who will lead them or what policy position they will take," she said.

"But we will be there to basically drive them to hold the line on climate."

Senator Milne accused Mr Abbott of not caring about climate change by saying he would abandon the 5 per cent emissions reduction target if his $3.2 billion direct action policy does not lead to the promised cut.

"I cannot believe he stands up with his daughters on stage and he doesn't care about global warming because that means he doesn't care what happens to them in 2050," she said.

The Greens released advice from the Clerk of the Senate, Rosemary Laing, indicating it would be hard for the Coalition to stop the $10 billion Clean Energy Finance Corporation's work without changing legislation.

The failure to pass the CPRS before Mr Rudd's downfall as prime minister in 2010 still ignites anger in the Labor Party.

Finance Minister Penny Wong, who held the climate portfolio at the time, said in July that the Greens should be held responsible "for their destructive impact on climate policy over these last years".

And last month, at a leaders' forum in Brisbane, Mr Rudd said Mr Abbott's Coalition and the Greens "hopped into bed and killed the Emissions Trading Scheme".

But Senator Milne criticised Labor for trying to negotiate with the Coalition rather than the Greens over the package "because they wanted to brown down the scheme".

At the time Labor needed the support of either the Coalition, or all of the Greens plus crossbenchers Steve Fielding and Nick Xenophon, to pass legislation in the Senate.

However, two Liberal senators, Sue Boyce and Judith Troeth, crossed the floor to support the carbon package in a Senate vote in early December 2009 following Mr Abbott's ousting of Malcolm Turnbull as Liberal leader.

Senator Milne told the National Press Club on Wednesday she could work with an Abbott government on several issues including improving the Coalition's paid parental leave scheme.

She backed Mr Abbott's position that leave should be paid at the mother's normal wage, but said the $150,000 salary cap was too generous and the Greens would work to rein it in.