THE Greens risk a backlash from many of their supporters after forging a controversial preference deal with mining magnate Clive Palmer.

Despite calling for a ban on new coal mines, the Greens have quietly announced they will put the Palmer United Party ahead of Labor and the Coalition in a raft of lower house seats.

The Senate balance of power party has also ironed out a Senate preference deal with Mr Palmer - a move designed to help South Australian Greens' Senator Sarah Hanson-Young win her seat.

Sarah Hanson-Young hangs up on 2GB's Ben Fordham

Palmer United Party disendorse a candidate

The controversial preference swap comes just days after Tony Abbott announced plans to put the Greens last on Liberal Party how to vote cards.

News_Rich_Media: Clive Palmer to make cameo appearance on Wednesday Night Fever

Clive Palmer's Titanic booklet includes CD update

But Mr Palmer, who has over 25 years experience in the Australian resources industry and has negotiated multi-billion-dollar coal deals with China, has defended his deal with the Senate balance of power party ahead of next month's poll.

"The parties are free to preference anyone. That is part of the democratic system," Mr Palmer said.

Voice of Australia: Federal Election 2013

The Greens - who are under challenge in at least three Senate positions and in the seat of Melbourne - are sending mixed messages to their supporters.

On the one hand, they are urging voters to "preference progressive minor parties" while also forging a preference swap with Mr Palmer.

News_Image_File: A friend of The Greens ... Mining magnate Clive Palmer.

Greens' campaign co-convener Ben Spies-Butcher said the actions by Kevin Rudd and Tony Abbott on asylum seekers makes this a "defining issue" at the election.

This has led the Greens to place the Palmer United Party ahead of the Liberals in the Senate and before both major parties in some lower house seats.

"Clive Palmer's support for further coal expansion remains anathema to the Greens, unfortunately it is support matched by the old parties," Mr Spies-Butcher said.

Senator Hanson-Young is struggling to retain her South Australian seat against a strong showing by independent Nick Xenophon. Senior SA political figures believe Senator Xenophon could pick up two Senate seats - squeezing out his Greens' rival.

Last night, he hit out at the deal with Mr Palmer. "This is desperate stuff - the Greens and a mining magnate doing a deal together," Senator Xenophon said.

On its official campaign website, the Greens slam the "old parties" over their support for coal mining.

"Labor has never said no to a coal mine expansion or coal seam gas project, and plans to massively increase coal exports through the Reef, as does the Coalition," the Greens site said.

"They also give billions of dollars each year to big mining companies to find and burn more fossil fuels; this tilts the field against clean energy and a safe climate.''

ends

###