Former foreign minister Kevin Rudd has confirmed he will challenge Julia Gillard in a leadership ballot on Monday morning.
Mr Rudd made the announcement at a feisty press conference in Brisbane at about 2.40pm AEDT this afternoon.
"Julia has lost the trust of the Australian people," he said.
"I want to finish the job I was elected to do."
Mr Rudd said Labor was heading for an election defeat, handing power to Tony Abbott and what he described as "the most right wing government in Australia's political history".
"All indications are that we're heading for the rocks at the next election," Mr Rudd said.
"If things don't change on Monday, I'm convinced that will be a certainty."
The former prime minister focused his criticism on the opposition leader, branding him as a man whose views "lie right at the extreme".
"He is a man with both feet planted firmly in the past," Mr Rudd said.
"His values are always cast in negative terms, and his positions are just extreme in his attitude to women and his attitude to climate change."
If defeated in Monday's leadership spill, Mr Rudd said he would go to the backbench and would not challenge Ms Gillard again.
He said the argument that the government's problems existed because of him was "unsustainable".
"I'm a bit tired and fed up of this frame that says if the Prime Minister has a problem, ipso facto, it must be me," he said.
"It wasn't K. Rudd who made a pre-election commitment on the carbon tax."
Mr Rudd called for a "truly secret ballot" in Monday's leadership spill and for Ms Gillard to assure members that no-one would face a preselection challenge for voting against her.
Several members of the Labor caucus have come forward to announce their support of Mr Rudd.
But current estimates favour Ms Gillard to retain the prime ministership.