Prime Minister John Key says Australia's uranium industry and close United States defence ties are factors behind reports Australian diplomats under Tony Abbott's Government worked to undermine a New Zealand-led push for nuclear disarmament.
New Zealand has been at the forefront of a 16-country push for a ban on nuclear weapons on humanitarian grounds. Australia has refused to back that on the grounds it would be counterproductive to other disarmament initiatives.
But Australian diplomatic cables, documents and emails obtained by the Sydney Morning Herald suggest the country's reliance on the US nuclear deterrent as a major plank of its defence strategy was the major factor in its opposition.
"It's kind of inevitable we might take a slightly different stance to a country like Australia that produces uranium and is part of Anzus," Mr Key said yesterday.
"It's just one of those things where they come from a slightly different perspective. They are part of Anzus, there's just different factors that might play into their thinking when it comes to nuclear disarmament."
Australia in October refused a New Zealand request to endorse a 125-nation joint statement at the UN highlighting the humanitarian consequences of using nuclear weapons.
Australia took exception to the statement's wording that it was in the interests of humanity that nuclear weapons were never used again "under any circumstances".
But Mr Key said it was "dangerous" to interpret that as a tacit statement from the Australian Government that the use of nuclear weapons could be justified in some circumstances.
"I don't think the Australians are arguing a nuclear war is in anyone's interests anywhere but they have a slightly different perspective on matters."
He could not see a scenario where the use of nuclear weapons to defend New Zealand could ever be justified.
The New Zealand-led campaign seeks to apply a similar international prohibition on the use of nuclear weapons as already exists for chemical and biological weapons.
But Australia's Foreign Affairs Minister Julie Bishop has been reported as saying that approach was counterproductive.
"The reality is that disarmament cannot be imposed this way," the Sydney Morning Herald reports her as saying. "Just pushing for a ban would divert attention from the sustained, practical steps needed for effective disarmament."
But the recently declassified documents reveal the Australian Government's main concern was that a nuclear weapons ban would "cut across" Australia's dependence on the US nuclear arsenal as a key part of its defence position.
An Australian Foreign Affairs and Trade Department document endorsed by Ms Bishop last year says a nuclear weapons ban "conflicts with Australia's long-standing position that, as long as a nuclear weapons threat exists, we rely on US nuclear forces to deter attack on Australia".