Former foreign minister Bob Carr is expected to resign within days, after Opposition Leader Bill Shorten unveiled a shadow frontbench without the former NSW premier.
Deputy leader Tanya Plibersek will take on the foreign affairs and international aid portfolio in a Labor frontbench that combines experienced hands with some of the party's rising stars.
Mr Shorten said he had spoken with Senator Carr last week, but declined to comment further.
"I can't add anything more to what he's said on the record," the opposition leader said.
Senator Carr was recruited by former prime minister Julia Gillard 18 months ago to fill a vacancy triggered by the retirement of minister Mark Arbib.
The NSW Labor administrative committee is expected to elect former lower house MP Deb O'Neill to fill the casual vacancy, which will then require the endorsement of a joint sitting of both houses of the NSW state parliament.
Ms O'Neill could be endorsed in time for the first post-election sitting of the federal parliament on November 12.
Senator Carr, who has kept a low profile for the past month, was re-elected at the September election for a six-year term starting on July 1 next year and will technically need to resign both the current term and the next.
Mr Shorten described his new team as "energetic and diverse", with women comprising almost half the frontbench.
Chris Bowen has retained the treasury portfolio, saying he has "unfinished business".
But former finance minister Penny Wong has moved to trade and investment and Tony Burke, the opposition's manager of business, has been appointed finance spokesman.
Deputy Senate leader and former communications minister Stephen Conroy takes on defence.
Leadership runner-up Anthony Albanese kept his preferred role as transport and infrastructure spokesman, adding tourism to his responsibilities.
Mr Shorten added science and small business to his duties in a bid to make both areas a focus for Labor over the term.
Among the more significant promotions were Catherine King (health), Shayne Neumann (indigenous) and Andrew Leigh (assistant treasury).
In the wake of former minister Nicola Roxon describing Kevin Rudd as a "bastard" ousted in an act of "political bastardry", Mr Shorten called for an end to disparaging comments.
"The Labor party needs to focus on the future," he said.
"We've got a great and energetic team, it reflects values and diversity and experience."
One of the priorities for the shadow cabinet, which meets in Canberra on Monday afternoon, will be Labor's stance on coalition legislation to abolish the carbon tax.
Mr Shorten said Labor would stick to the principle of an internationally-linked price on carbon as the best way to address climate change.
"We don't change our views, we are not a weather vane on climate change," he said.
"In terms of our specific policies, we will work on them in the lead up to the next election."
Labor went to the election having promised to "terminate" the carbon tax and bring in an emissions trading scheme from July 1, 2014.
Veterans' Affairs Minister Michael Ronaldson criticised the appointment of South Australian senator Don Farrell as his shadow counterpart, who will also have responsibility on the Labor side for the centenary of ANZAC in 2015.
Senator Farrell lost his seat at the recent federal election, so his term expires at the end of June - a year before the centenary's celebration.
"The appointment of Senator Farrell ... is an extraordinary decision which is more about political convenience than competence and conviction," Senator Ronaldson said in a statement."Australia's veterans deserve better than this."