New Labor leader Kevin Rudd says the negativity and destructive politics at the federal level must stop.
Mr Rudd said politics in recent times had "failed the Australian people" and he was driven by a need to secure the nation's future.
"I simply do not have it in my nature to stand idly by and allow an Abbott government to come to power in this country by default," he said.
"I recognise that Mr Abbott is a man steeped in the power of negative politics and he is formidable at negative politics.
"But I see no evidence of a real positive plan for our country's future."
Mr Rudd also thanked outgoing treasurer Wayne Swan for his contribution to the government.
He said he had worked "intimately" with Mr Swan in 2008-2009 to prevent the country from rolling into the global economic recession.
"So Wayne, whatever our differences have been, I acknowledge that contribution here as part of that team which kept us out of global catastrophe," Mr Rudd said.
New Labor deputy leader Anthony Albanese said he had a big job to do.
"I will do it with enthusiasm, passion and commitment and give my all for the cause of Labor," he said, standing side by side with Mr Rudd.
"It is only Labor governments, I believe, that can truly serve the long term interests of the nation."
Mr Albanese said on Wednesday night the party had maximised its chances of going into a third term of a Labor government.
He paid tribute to Ms Gillard and Mr Swan for their achievements and for their efforts in ensuring Labor was able to govern since the hung parliament in 2010.
Mr Rudd issued a call to Australia's youth, many of whom he said had shunned an interest in the nation's political system.
"I understand why you've switched off, it's hardly a surprise," he said.
"But I want to ask you to please come back and
"We need you, we need your energy, we need your ideas, we need your enthusiasm and we need you to support us in the great challenges which lie ahead for the country.
"And with your energy, we can start cooking with gas."
Mr Rudd said that he and Mr Albanese had been briefed by the Department of Prime Minister and Cabinet.
"We will begin our briefings as appropriate in the next several days on the budget and the economic outlook and on a range of other international matters that lie before us," he said.
As to when he would be sworn in as prime minister, Mr Rudd said he would await advice."We will await the Governor-General on that matter," he said.