Opposition Leader Tony Abbott has gone on the attack after hearing Kevin Rudd will work part-time for the United Nations.
The former prime minister has been appointed to a new 21-member panel on global sustainability, a decision announced by UN secretary-general Ban Ki-Moon in New York overnight.
"It's now official, former prime minister Rudd does have a part-time job with the United Nations," Mr Abbott told reporters in Sydney on Tuesday.
The appointment put yet another question mark over the make-up of Labor's next ministry.
"What it means is that this government's ministry is in complete flux," Mr Abbott said.
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Labor was losing its "two best ministers" in outgoing Finance Minister Lindsay Tanner and Defence Minister John Faulkner.
Mr Abbott also questioned a possible deal over the foreign portfolio, saying a deal might have been struck for Mr Rudd to replace Stephen Smith.
It left a ministry in which the next finance, defence or foreign minister could not be named ahead of polling day, he said.
Mr Abbott said Labor was delivering the prospect of part-time ministers. Environment Minister Peter Garrett had been one for months, he said.
Mr Rudd has defended his decision to take up the position.
"This appointment is entirely consistent with Mr Rudd's work as a member of parliament should he be re-elected at the coming election," his spokesman said in a statement.
The panel's first meeting will be held in about one month's time, which is likely to be only meeting this year, while there should be another two in 2011.
Mr Rudd, who will not be paid, had a "strong commitment to building on the international agreements on climate change," the statement said.
The panel is expected to deliver its final report by the end of 2011, ahead of the 2012 UN conference on sustainable development in Rio de Janeiro.
Prime Minister Julia Gillard wasn't buying Mr Abbott's attack on Labor's so-called "part-time ministers".
"He's probably trying to avoid answering questions on this (the economy) today, and so talking about other matters," she told reporters in Adelaide. She did not comment on Mr Rudd or his new role.
