Labor will switch back to Kevin Rudd before the September election, according to former opposition leader Malcolm Turnbull.
''I think it is likely they will put him back,'' Mr Turnbull, the opposition's communications spokesman told ABC Television on Thursday.
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Rudd icy on challenge
Former PM Kevin Rudd has waved away opposition taunts that he's making a prime ministerial comeback. Mark Kenny assesses Labor's troubled start to the election year.
''The Gillard government goes from one catastrophe to another.''
But Mr Rudd has ridiculed the suggestion, saying Mr Turnbull should ''jump in the ice bath''.
''I said a week or so ago everyone should take a long cold shower,'' Mr Rudd told Channel Seven on Friday morning. ''What I'd say to Malcolm and you Joe (Hockey) is it's time to jump in the ice bath''.
On the speculation by Mr Turnbull – ''who has no leadership aspirations himself'' – which was forming the basis for a discussion on whether he would challenge again for the leadership, Mr Rudd responded ''give me a break''.
Mr Turnbull was an opposition leader during Mr Rudd's tenure as prime minister. He was removed by the Coalition and Tony Abbott elected to replace him.
Labor's standing in the electorate fell in the most recent Newspoll, with the Coalition having a 12-point buffer in the two-party-preferred vote.
Mr Turnbull has consistently been nominated by voters as the preferred opposition leader over Mr Abbott while polls have shown that Mr Rudd is preferred as PM over Ms Gillard.
A spokesman for Mr Turnbull refused to comment when asked about the chances of Mr Turnbull reclaiming the Liberal leadership given the poll results.
Most recently, independent MP Tony Windsor said the Coalition would definitely win the election if Mr Turnbull was leader, but was circumspect when asked if Labor could win if it replaced Prime Minster Julia Gillard with Mr Rudd.
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Workplace Relations Minister Bill Shorten said having Mr Turnbull offer commentary on the Labor Party was like asking rival sports teams to have inside information on each other.
''I'm sure there is a lot of Carlton cheer squad members who have got their ear to the ground about what Collingwood is doing, but I do take it with a grain of salt,'' he told the Nine Network.
''Australians this year want to see a competition of ideas, not just personalities.''
Mr Shorten said he was certain Ms Gillard would lead Labor to the next election.
Mr Turnbull also commented on the mining tax, saying the government had made a mess of it.
Federal Treasurer Wayne Swan was criticised in parliament this week for his handling of the minerals resource rent tax (MRRT).
The tax's revenue was $126 million for the six months to December, short of the $2 billion forecast for this financial year.
''The fate of the mining tax is colossal,'' Mr Turnbull said.
The Labor government switched to Ms Gillard as leader in June 2010, and she subsequently defeated Mr Rudd in a leadership challenge in February 2012.