Tony Abbott, elected the Commonwealth country's 28th prime minister last year, became the latest international leader to wade into the debate after US president Barack Obama said his administration had a "deep interest" in ensuring the United Kingdom remained united.
Mr Abbott, who spent two years at the University of Oxford, told the Times: "What the Scots do is a matter for the Scots and not for a moment do I presume to tell Scottish voters which way they should vote.
"But as a friend of Britain, as an observer from afar, it's hard to see how the world would be helped by an independent Scotland.
"I think that the people who would like to see the break-up of the United Kingdom are not the friends of justice, not the friends of freedom, and that the countries that would cheer at the prospect of the break-up with the United Kingdom are not the countries whose company one would like to keep."
The Yes campaign believes the nation would be strengthened by independence but the UK government is opposed to the breakaway.
A Yes Scotland spokesman said: "Independence seems to be working well for Australia.
"These comments have echoes of Lord George Robertson's "forces of darkness" speech in April which was widely ridiculed, even by No supporters, as one of the anti-independence campaign's most outlandish scare stories.
"The decision about Scotland's future is one for the people of Scotland to make - a point that even David Cameron asserts. After a Yes vote, Scotland will take her place as a normal and valued member of the international community - just as Australia did when she gained independence at the turn of the century."
A spokesman for First Minister Alex Salmond said: "Tony Abbott has a reputation for gaffes, but his bewildering comments have all the hallmarks of one of the Westminster Government's international briefings against Scotland.
"Seventy-one nations and territories were represented at the recent Commonwealth Games in Glasgow but only Mr Abbott has put his foot in it. Many Australians, including the great number with close Scottish connections, will look on in bafflement at these remarks - Australia is a country that has gained its independence from Westminster and has never looked back.
"Scotland's referendum is a model of democracy, which has been cited as such internationally, including by the US Secretary of State. An independent Scotland will be a beacon for fairness, justice and cooperation in the international community - and a great friend of Australia."