Prime Minister Julia Gillard sinking as the Greens jump ship THE Greens have torn up their formal alliance with Julia Gillard in a dramatic political dummy spit that the Prime Minister's internal enemies appear intent on using to bolster their case for a leadership change. With the PM's job already on the line following a growing split in her caucus, it was her coalition partners yesterday who stuck the knife in by ripping up the minority party's formal agreement with Ms Gillard. In a desperate move to arrest its own declining vote and distance itself from an increasingly unpopular Labor government, Greens leader Christine Milne claimed her party had been betrayed by the PM over the mining tax. But the political divorce appeared to ring hollow. Ms Milne claimed she would not bring down the government, promising to still guarantee supply and confidence in the government in the parliament. Labor strategists were left in no doubt the move was part of a blatant political strategy by the Greens to cut its ties so it could compete with Labor for the left-wing primary vote. One senior minister likened the move to a sign the Greens had moved to "another planet," claiming it would only further damage the Greens and help Labor recover some of the middle ground. "This is a meaningless act of petulance from an immature political party," Transport Minister Anthony Albanese said. They are saying of themselves that they don't inhabit the real world. Ms Milne announced the split at the National Press Club yesterday, shortly after 1pm. She phoned Ms Gillard 20 minutes before she was to give her speech, while the Prime Minister was on her way to a lunch in Melbourne. Ms Milne said it was Labor that had dishonoured the alliance by siding with the "big miners" and refusing to rework its failed mining tax. "By choosing the big miners the Labor government is no longer honouring our agreement to work together to promote transparent and accountable government, the public interest or to address climate change," she said. Well, so be it. Ms Gillard's office issued a curt response. This is a matter for Christine Milne and The Greens. "We will always be the party that puts jobs, growth and work first," it read. While some Labor figures were privately rejoicing at the formal break with the Greens, Labor MPs agitating for a return to Kevin Rudd claimed the split could be viewed by many voters as a case of the "rats leaving a sinking ship." "Having the Greens abandon the PM is the ultimate act of humiliation," one Rudd backer said. They are the only political entity who are more unpopular than us. With leadership tensions refusing to subside, other senior Rudd backers claimed that, having the Greens end an alliance which should have been torn up by Labor, Ms Gillard would be further exposed in the caucus. Ms Milne last night would not comment on whether the Greens were now in preference discussions with the Liberal Party, over seats such as Melbourne, held by the Greens' only MHR, Adam Bandt. Online bookmakers reported a plunge on Mr Rudd with him now favourite to lead Labor to the September 14 election. "We just took our biggest single wager on Rudd to be PM at the next election since we commenced betting on this market last June," Sportingbet CEO Michael Sullivan said. He's been backed from $2.40 into $1.70. Adam Brandt, Bob Brown, Sarah Hanson-Young, Christine Milne and Lea Rhiannon have 'moved to another planet', according to a senior ALP figure.