The Liberal Party changed leaders because of a clear policy difference, but Labor's ousting of Kevin Rudd had no such reasoning behind it, former prime minister John Howard says.
Mr Howard said the government of Prime Minister Julia Gillard, who won a challenge against Mr Rudd in 2010, was haunted by Labor's failure to explain the move.
Opposition Leader Tony Abbott became Liberal leader, toppling Malcolm Turnbull, because he took a stand to drop the opposition's support for an emissions trading scheme, Mr Howard told a finance conference on the Gold Coast.
"For Tony Abbott to turn around now and say, `Oh no, I've changed my mind and I'm going to support the government's policy,' would be to break faith with the majority of his own colleagues who made him leader because he had a different attitude to Malcolm Turnbull," Mr Howard said.
"Now whether you agree with Abbott or Turnbull, the principle at stake there was that the leadership of the Liberal Party changed on a policy issue.
"The leadership of the Labor Party did not change from Rudd to Gillard on a policy issue, and that's the reason why they still can't explain it and why it continues to haunt the Labor Party."
Mr Howard made no mention of the attack launched on Friday against Mr Turnbull by recently retired federal coalition powerbroker Nick Minchin, who backed Mr Abbott's leadership bid.
In a letter to The Australian newspaper, the former Liberal senator said Mr Turnbull's utter preoccupation with Liberal conservatives revealed his inability to get over losing the leadership late in 2009.
"Turnbull has only himself to blame for the failure of his year-long leadership," Mr Minchin wrote.
"It was his deficiencies as a leader - not those terrible conservatives - that led to his demise."
Mr Howard also told delegates at the Financial Services Council annual conference Australians were starting to feel nervous amid fears of another global economic downturn.
"There is still a sense of optimism in many parts of Australia that one doesn't find in the United States and that one certainly doesn't find in many countries in Europe.
"But it's an optimism that is starting to fray and dwindle."
