The Australian Greens' leader Christine Milne has appealed to voters not to allow the Coalition to take control of both houses of parliament in next month's election.
She made the appeal as the Greens officially launched their election campaign in Canberra.
As Zara Zaher reports, the party's policy priorities include environmental protection, better treatment of asylum seekers, and housing affordability.
Opinion polls continue to show the Coalition with a lead over Labor and on track to win the September 7 election.
Greens' leader Christine Milne says if the Coalition wins, it would only require another three seats in the Senate to gain control of both houses of parliament.
Senator Milne says a strong Greens voice in the parliament will ensure the major parties don't have complete control.
"The Greens stand between Tony Abbott and the kind of future that we envisage, caring for people and the environment. So can I suggest that voting Green is double value voting. Not only does it return the Greens but it stops Tony Abbott getting absolute power in the federal parliament."
Senator Milne says the Coalition and Labor Party should be condemned for their approach toward asylum seekers.
She has pledged the minor party would push for a Senate inquiry into the treatment of asylum seekers, taking evidence from international human rights and legal experts.
She says former Prime Minister Paul Keating's description of the Coalition as "mean and small" applies equally to the Labor Party.
The Greens leader says the cruelty to shown to asylum seekers by the major parties is the defining issue of this election campaign.
"The old parties are leading us into a legal quagmire and international shame with their willingness to play politics with the lives of people seeking asylum. That Labor can give up on such basic human principles and human rights in the rush to an election is the clearest evidence yet that they can no longer be trusted to stand up for what matters but will do whatever it takes to claim power."
Senator Milne used the campaign launch to outline the Greens' policies highlighting the needs of Indigenous people, the environment, single parents, marriage equality and small business.
She says the Greens would also push for a Clean Air Act to set up national rules about pollution.
"The Greens are already standing with communities all over Australia to say no to coal seam gas, no to expanded coal seam gas, no to expanded coal mining and yes to the health of our farmlands and our ground water systems. The Greens will establish a Clean Air act to lower pollution and improve our health by requiring the development of national standards and regulations for air quality, starting with better regulation of air quality from coal mines and coal fired power stations, requiring coal trains that pass through population centres to be covered and driving the installation of an air quality monitoring network capable of providing real-time data on pollution sources."
Senator Milne has also announced a proposal to extend the national rental housing affordability scheme.
Senator Milne says she is confident the Greens will do well at the election, and that the party's only member of the House of Representatives, Adam Bandt, will retain his seat.
Mr Bandt holds the seat Melbourne on a margin of 6 per cent, but he's been disadvantaged this election by a Liberal Party decision to put him last on its how-to-vote cards.
Opinion polls indicate that Greens Senators, including immigration spokeswoman Sarah Hanson-Young, also face an uphill battle to be re-elected.
