Senior Labor MP Jenny Macklin has announced her support for leadership aspirant Anthony Albanese, saying the former deputy prime minister's record in government makes him best placed to defeat Tony Abbott.
In a brief statement, Ms Macklin said Mr Albanese had proven himself a "terrific parliamentary performer, a skilled communicator and a passionate advocate for working people".
"I strongly believe that under Anthony's leadership, Labor can defeat Tony Abbott at the next election," the former families minister said on Thursday.
"His record in government - as a cabinet minister and as the Leader of the House - make him the best candidate to hold Tony Abbott to account over the next three years."
Mr Albanese and Mr Shorten are contesting the Labor leadership, which will be settled in October by a ballot giving caucus and ordinary ALP members given an equal say in the outcome.
Acting opposition leader Chris Bowen, a member of the right faction which is backing Mr Shorten, dismissed suggestions people would be voting along factional lines.
Mr Albanese is a powerful figure in Labor's left.
"I'm aware of rank and file members and caucus members who'll be voting for the candidate that they think is the best for the job," Mr Bowen told ABC Radio.
"It might not necessarily be a member of the same faction they would support."
Mr Albanese took his leadership campaign to Brisbane on Wednesday night, telling supporters his loyalty made him the best man for the job.
Mr Albanese landed a solid blow against his right faction powerbroker opponent, who was instrumental in ending the prime ministerships of both Kevin Rudd and Julia Gillard.
"We should not be shy about defending the interests of Kevin Rudd and Julia Gillard and I am in a position to do both because I was loyal to both," Mr Albanese told a supportive crowd at The Melbourne Hotel in Brisbane's West End.
"I woke up each and every day and did my best for the cause of Labor. I didn't engage in internal shenanigans."