Former Labor leader Bill Shorten has hit out at what he has described as "powerful vested interests" that campaigned against his party.
The former opposition leader addressed Labor's first Caucus meeting since its shock election defeat, in which the party installed Anthony Albanese as his replacement.
Mr Shorten said Labor needed to learn from its loss but external factors had conspired against the ALP.
"I understand that there are lessons to be learned from defeat," Mr Shorten told Labor's Caucus meeting.
"Rather than commentators' snap judgements or hindsight masquerading as insight, it is important that we take our time to reflect.
"But obviously we were up against corporate leviathans — a financial behemoth — spending unprecedented hundreds of millions of dollars [on] advertising, telling lies [and] spreading fear."
Mr Shorten also took aim at the media, parts of which he accused of not wanting a Labor government.
During the campaign he singled out News Corporation's The Daily Telegraph for its attacks on him and his family.
At the time, he fought back tears when he accused the paper of using his mother's life as a political attack on him.
"Powerful vested interests campaigned against us, through sections of the media itself, and they got what they wanted," Mr Shorten said on Thursday.
"And I understand that neither of these challenges disappeared on election night. They're still out there for us to face.
"It is important we face them with courage and honesty, with principle, and unity."
Mr Shorten was opposition leader for six years, beating Mr Albanese for the role in 2013.
He will now sit on Mr Albanese's frontbench in a role that is yet to be announced.
"I have been privileged to have all of your encouragement, your generosity, your decency and your support," Mr Shorten said.
"I am deeply grateful for that."
Mr Shorten's deputy, Tanya Plibersek, will remain on Labor's frontbench but will not serve in its leadership.
Victorian Richard Marles is set to replace her as deputy leader.
"I pay tribute to Bill and to Tanya. These two giants of our movement have fought for the cause of Labor their entire lives," Mr Albanese told his Caucus.
"No-one could have done more to try to get us in the room where we want to sit, after the next election."
He said both would have "significant roles to play" in his shadow ministry, which he said he would announce within days.
