The Greens leader, Christine Milne, has suggested Tony Abbott is not fit for leadership because of his stance on climate change, but she is preparing a Democrats-style “keep the bastards honest” election campaign to stop Abbott’s “excesses” in the Senate, on the assumption he will be prime minister.

In an interview with Guardian Australia, Milne said the Liberal leader’s personal politics were threatening the planet. “Tony Abbott has been so irresponsible in terms of addressing global warming,” she said. “He has chosen to jeopardise the future of children, of generations henceforth, of species, by putting his own political perspective ahead of actually addressing global warming.

“I would argue nobody is fit for leadership if they choose to politically exploit an issue which jeopardises the wellbeing of the whole community and the environment into the future,” she added. “That is something for which they have to take personal responsibility.”

The Greens will appeal to voters to deliver them the balance of power in the Senate as a check on an Abbott government.

Asked whether the old Democrats slogan “keep the bastards honest” summed up the Greens’ 2013 election tactics, Milne said: “That’s absolutely right. The opinion polls have been consistent for some months: the country is going conservative and it is pretty clear that there will be an an Abbott government.”

“Our focus is to position the Greens in stopping Tony Abbott getting control of both houses of parliament,” said Milne. “The positioning for the Greens at this election will be: the Greens are the strong alternative voice you need in the Senate to prevent the excesses of an Abbott government.”

But, on current polling, maintaining the Senate balance of power will be a fight for the Greens. The collapse in Labor’s vote means the Coalition might be able to pass legislation through the Senate with the support of a group of conservative-leaning minor party or independent Senators, or possibly even in its own right.

“I think it is much more likely [Tony Abbott] would have control in conjunction with conservative independents [than in his own right] and that would be again a disaster for the country,” Milne said, pointing to independent senator Nick Xenophon’s vote against the carbon pricing legislation and his campaign against windfarms with Democratic Labor Party senator John Madigan.

Three of the Greens’ nine senators are up for re-election in the half-Senate poll and Milne said her job was to see them all returned, as well as to pursue “an outside chance” that former GetUp! director Simon Sheikh would take an ACT Senate seat.

“That seat, the last seat in Western Australia and South Australia and the last seat here in Canberra will be a choice between the Greens and the conservatives, so our job is to say to people: you are choosing between an Abbott person in the Senate or a Green in the Senate and that will be the battleground of the campaign,” she said.

Milne also insisted she would “work in co-operation with whomever is the prime minister of the day”, including Abbott.

“That has always been my position,” she said. “I don’t have to agree with them, I don’t have to like them, but I do have to work with them and I would do that and I have done that in the past,” she said, referring to her time in the Tasmanian parliament.

Asked on which issues she would be able to co-operate with a future Coalition government, she nominated Abbott’s paid parental leave scheme, but then pointed to policies where she would seek to change the Coalition’s stated position, including Labor’s proposed $2.8bn cuts to tertiary education, which the Coalition has supported.

She said Abbott “has shown that if there is a sufficient public outcry he is prepared to back off and I would be hoping we can work with him to secure an abandonment of cuts to universities”. She added: “While he has said he supports the cuts to universities – it was a Labor party proposition that he is prepared to go along with – the feedback in the community is intense in opposition to it and I think there is a likelihood we could work with [an Abbott] government to stop the cuts to universities.”

And she said she would support “revenue measures” to help a Coalition government pay for its promises and reduce the deficit but would not necessarily support the Coalition’s promised spending cuts.

“They won’t necessarily get the support for those [spending cuts] if the Greens hold the balance of power in the Senate. We will talk about where to raise revenue but they will have to back off some of their more extreme positions because they are not going to get parliamentary support,” she said.

Milne defended the Greens’ push for a much higher carbon price during the negotiations over the clean energy package. She said that the Greens’ position was based on what was needed to drive Australia’s contribution to international efforts to limit global warming to 2C.

She conceded the international price was forecast to be much lower than Australia’s at the point when the Australian price starts to be set by the market, but said she had “faith” the European Union would fix the problems driving down its carbon price.

“If you look at the European price as it stands today, yes, you would definitely say there will be dislocation because we are going from a higher price to a lower price, which is why so many businesses are saying bring it on, bring it forward because we want the lower price. But the reality is the world needs to bring down emissions faster and the European Union is going to have to fix the problems. I am putting my faith in the Europeans getting their act together,” she said.

And she vigorously defended the Greens’ opposition to any new coal mines in Australia, even if other countries continued mining.

“It is quite stupid to put all the future of Australia’s wellbeing in the hands of the resource-based industries. That is a dumb strategy. You can’t just sit here and say other people are going to develop their coal mines so we’ll develop our coal mines. The world cannot have that amount of coal being sent to the atmosphere, so we have to leave our coal in the ground and diversify our economy, and that’s why we need to take a lead, and that’s why as a country we are disadvantaging ourselves if we try to stretch out the fossil fuel era when we know damn well it is gone,” she said.

The Coalition currently holds 34 seats in the 76-seat Senate and needs 39 seats for a majority. There is currently one independent, Xenophon, who is up for re-election and is expected to retain his seat. There is one DLP senator: Madigan.

Only half the Senate faces the voters in a half-Senate election and the plethora of emerging minor parties and independents, including Katter’s Australian party, the Palmer United party and Pauline Hanson – and the requirement for complicated preference deals – make the 2013 outcome difficult to predict.

The newly-elected senators take their seats on 1 July 2014. The existing Senate sits until then. There are three Greens senators up for re-election: Sarah Hanson-Young is contesting this election in South Australia, Scott Ludlam in Western Australia and Peter Whish-Wilson in Tasmania.