Bill Shorten's future depends on how he performs at the unions royal commission, says a senior Labor figure.
The federal opposition leader has agreed to front the inquiry on July 8 during parliament's winter break, rather than August or September as previously scheduled.
Former Queensland premier Peter Beattie said it would be an important test for Mr Shorten.
"If at the end, under oath, he can't answer the questions then he is politically finished. No doubt about it," Mr Beattie told the Seven Network on Friday.
However, Labor frontbencher Anthony Albanese says he's confident Mr Shorten will survive allegations surrounding his time as an Australian Workers Union boss.
"Bill Shorten will certainly lead us to the next election," Mr Albanese, who was the other contender for the leadership after the last election, told the Nine Network.
Mr Shorten was elected Victorian secretary of AWU in 1998 and national secretary in 2001, before winning a federal seat in 2007.
The royal commission has heard evidence about a series of deals, relating to training schemes and membership dues, between the AWU and companies which bolstered the union's coffers.
Supporters of Mr Shorten say he was instrumental in delivering lucrative pay deals for workers while helping construction and infrastructure companies complete important projects.
Mr Albanese said Mr Shorten had a proud record as a union leader.
Prime Minister Tony Abbott told reporters in Cairns on Friday the opposition leader had a lot of explaining to do.
"I'm all in favour of arrangements between workers and managers to maximise the ability of businesses to get on and do jobs and succeed," Mr Abbott said.
"What I'm not in favour of is anything that is dishonest, that rips off workers to benefit union bosses."
One of the key issues was the use of "ghost members" to inflate union membership and deliver them more power within Labor, he said.
"Power inside the Labor Party seems to be more important to these people than the actual benefits to workers."
