Australia's former Human Rights Commissioner turned Liberal MP Tim Wilson has claimed Kevin Rudd is a "known bully" who did not deserve the role of being the United Nations Secretary-General.
Mr Willson told Sky News Australia that we needed to "get off this unreality train that Tanya Plibersek and Bill Shorten are now on".
He described Mr Rudd as a "known bully". "That is what Kevin Rudd is," he said.
"And it's not based on my judgment, it's what Julia Gillard has said.
"That is what so many of her colleagues have said. Let's get real. Kevin Rudd was not an acceptable candidate. Kim Beazley was right about this too."
"I don't think we should be turning around to the Australian people ... and saying bullying behaviour and bullying conduct and bullying character is something that should be rewarded and put on the international stage to represent us."
His comments come after Senator Pat Dodson, Professor Tom Calma and about a dozen other indigenous leaders have spoken out in favour of Mr Rudd.
They say it was "a true disappointment" his nomination for secretary-general of the United Nations was not endorsed by Prime Minister Malcolm Turnbull.
"The man who delivered the Apology is a man suitable for the post of Secretary-General of the United Nations," the group said in a statement issued on Sunday afternoon at the Garma festival in northeast Arnhem Land.
"Kevin Rudd has long demonstrated his commitment to First Nations Peoples. Under his leadership our Stolen Generations received an acknowledgement and apology for the hurt and trauma endured." They said he established closing the gap targets and remains committed to indigenous Australians.
"Kevin Rudd remains a friend and champion of First Nations Peoples and it is a true disappointment that his nomination for the UNSG has not been endorsed," the statement ended.
Earlier today, Labor frontbencher Ed Husic defended Mr Rudd's decision to release private letters from the prime minister showing Mr Turnbull had once backed his aspirations for the UN job.
Mr Husic said the correspondence needed to be in the public domain.
"This was not a decision made on merit," Mr Husic told Sky News.
"I think the public will rightly draw the conclusion that this was vindictive partisan politics."
Mr Husic's comments come as many Labor MPs have criticised Mr Turnbull for not officially backing Mr Rudd, though it is understood there are some Labor MPs who wouldn't back Mr Rudd either.
Special Minister of State Scott Ryan said he believed Malcolm Turnbull has shown more dignity than Labor over Mr Rudd's failed attempt to get nominated for the United Nation's top job.
"The prime minister has shown more dignity towards Kevin Rudd than most of his colleagues over the past three years," Senator Ryan told Sky News.
Opposition leader Bill Shorten has accused the prime minister of treating Mr Rudd in a "shabby fashion" for "petty politics" after he refused to endorse him.
Australia won't be nominating Mr Rudd for secretary-general of the UN even though he claims Malcolm Turnbull had told him Australia would be "mad" not to support him.
Mr Shorten echoed a comment by his senior minister, Anthony Albanese, labelling Mr Turnbull's actions "pathetic".
"He has squibbed the chance to be a leader for all Australians and all he's trying to do is paper over the divisions in the Liberal Party," Mr Shorten told reporters in Darwin on Saturday.
"And in the meantime, a distinguished Australian has been treated in a very shabby fashion for nothing more than, I think, petty politics.
"Malcolm Turnbull's actions are pathetic. They're disappointing."
Foreign Minister Julie Bishop and Attorney-General George Brandis are understood to have supported Mr Rudd's nomination, but several conservative ministers including Immigration Minister Peter Dutton and Treasurer Scott Morrison spoke against it.
Mr Rudd took to Twitter to thank Ms Bishop for her support, saying "unfortunately" the prime minister had disagreed. The prime minister said on Friday the government would not back the former Labor prime minister because he didn't believe he was suited for the role but refused to give details.
Late on Friday Mr Rudd released three letters he had sent to Mr Turnbull in which he refers to the prime minister's apparent support.
In the second letter, Mr Rudd said he was "shocked" the prime minister told him he no longer supported his bid after "You had always said to me that the Australian government would be `mad' not to support my candidature." He wrote another letter this week asking for a personal meeting to "simply ask for the right to be heard".
After Mr Turnbull announced his decision, Mr Rudd said it was a "pity" the government did not support him and that the prime minister would not explain the decision in person, even though they were both in Sydney at the same time.
"It would have reflected well on what our nation can offer to the world - as a middle power with relationships across the world, including the developing world, smaller states, the Commonwealth, our Pacific Island friends and of course our partners in Asia," Mr Rudd said in a statement.
But Deputy Prime Minister Barnaby Joyce said a person should not be backed for a top role just because he was Australian.
He told ABC television it was Labor who had poor character assessments of Mr Rudd.
Mr Turnbull said the decision had nothing to do with Mr Rudd being a former Labor leader, pointing to Kim Beazley's appointment as US ambassador.
It is possible Australia could back former New Zealand prime minister Helen Clark for the UN role.