A Charles Sturt University (CSU) politics academic says it's no surprise that the Turnbull government has blocked former Prime Minister Kevin Rudd's bid to lead the United Nations.

Associate Professor in political science in the CSU School of Humanities and Social Sciences Dominic O'Sullivan is not surprised by the Prime Minister's decision not to nominate Kevin Rudd for the position of Secretary-General of the United Nations.

Professor O'Sullivan (pictured) said this was always going to be an early test for the new Turnbull government and perhaps Mr Turnbull has made the decision with a view to consolidating his support within the Cabinet rather than alienate Coalition members.

"Given the turnover of Australian Prime Ministers in recent times, it's better for Mr Turnbull to annoy the Labor opposition by this decision than to risk further fracturing his own Coalition. One need only reflect on the plight of his predecessor, and indeed Mr Rudd's time as Prime Minister. This issue will quickly pass from political and public consideration and will not jeopardise Mr Turnbull's long-term standing with his party or the electorate."

Professor O'Sullivan said that it is common for governments to nominate former opponents for international positions and, indeed, the present conservative government of New Zealand is actively supporting the former Labour Prime Minister, Helen Clark, in her bid to become the next UN Secretary-General.

"The difference is that, beyond domestic political contests, Helen Clark attracts bipartisan international respect for her foreign policy expertise and diplomatic skills," Professor O'Sullivan said.

"In contrast, Mr Rudd has significant policy expertise and speaks Mandarin fluently but is a deeply polarising personality, and it is that, not that he is on the wrong side of politics that has cost him the nomination.

"The Australian Labor Party naturally lobbied the government on Mr Rudd's behalf, but given the views, on the public record, that Labor members of parliament have expressed about his personal attributes these were not endorsements of conviction.

"The position of Secretary General is well above domestic politics and so is the Prime Minister's decision on this occasion."

Professor O'Sullivan also reflected on future career options for Mr Rudd.

"Mr Rudd has an active public speaking and consulting role but having run the country it will be hard for him to find a new role comparable to the top job at the United Nations, 'running the world', so to speak," Professor O'Sullivan said. "Perhaps the international corporate world will beckon him."