Former prime minister Kevin Rudd has hit back at comments by one of his ex-colleagues that he was a "megalomaniac" who put Australia's safety in jeopardy. 
The accusations were made by former environment minister Peter Garrett on Channel 7's Sunday Night program, in what was billed as Mr Garrett's first substantial interview since leaving politics two years ago.
The interview coincided with the release of his upcoming memoir Big Blue Sky on Wednesday.
In one passage of the book, read by interviewer Melissa Doyle, Mr Garrett claimed the safety of Australia was potentially threatened while Mr Rudd was leader.
"It's a big call, but I stand by it," Mr Garrett said, adding the former Labor prime minister treated people with "an enormous amount of contempt" and made "the business of the country almost ungovernable".
When pushed on what danger he feared Mr Rudd posed, Mr Garrett said the former PM was "unpredictable" and he didn't know what he "could or would do".
"I mean, even with [John] Howard you know where he stood," he said.
"I'm not a great fan of John Howard's, and he wouldn't be a great fan of mine, but that aspect of his prime ministership I sort of understand and respond to."
On Monday morning, a spokeswoman for Mr Rudd rubbished the claims, denying they had any substance.
"Peter Garrett is trying to sell a book. I have no idea what else he's doing these days," the spokeswoman told Fairfax Media.
"If Mr Garrett were serious about these accusations he would have made them five years ago. Not try to rewrite history now."
In his time as environment minister, Mr Garrett was not a member of the cabinet's National Security Committee, which formulates strategies to deal with Australia's security and focuses on other classified matters, and would not have been privy to its decisions.
In another passage from the book, Mr Garrett wrote that supporting Mr Rudd was "certainly the biggest" mistake he made in his political career.
"I've been particularly strong in this book about leadership and Rudd's leadership and I think it needed to be said," Mr Garrett said.
"I'm critical of him, that's true, very critical, but I think for good reason."
Mr Garrett stepped down from politics in 2013, when Julia Gillard was ousted as prime minister.
Both Mr Rudd and Mr Garrett last year appeared before the royal commission into the former Labor government's home insulation scheme in which four installers died. Mr Garrett had originally been in charge of the scheme, but after the deaths Mr Rudd replaced him with Greg Combet, saying the former ACTU secretary had better experience with workplace safety issues.  
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