Prime Minister David Cameron has promised to hold such a referendum by the end of 2017 if he wins the next parliamentary election in two years' time, responding to public concerns about perceived EU meddling in domestic affairs and signs that those EU states that use the euro may opt for greater integration.
Australia's intervention follows calls from the United States and Japan for Britain not to sever its EU ties and suggests that Cameron's plan to give Britons a vote on the issue is causing unease with some allies.
France and Germany have signalled they want to keep Britain in but will resist it trying to "cherry-pick" the EU policies it likes and dropping those it does not.
Australia's contribution came in the form of a letter sent from the office of Foreign Minister Bob Carr published on the website of the British Foreign Office on Monday (22 July) as part of a review the government is conducting into the country's EU ties.
"Australia recognises the UK's strength and resilience and looks forward to seeing it continue as a leading economy and effective power," the letter said. "Strong effective membership of the EU contributes to this."
Australia valued the role that Britain played in shaping EU foreign policy, it added. "I hope to see this continue long into the future," the author, whose name and signature had been blanked out at the bottom, said.
A second letter sent from an unidentified individual based at Parliament House in Canberra said EU membership allowed Britain to better "leverage" its global influence and meant it was viewed as "a platform for trade and investment in the broader EU market."
"I encourage the UK to maintain its influence by remaining an engaged participant of the EU internal market," it said. With a market of 500 million people, the EU is Britain's main trading partner.
The British government said in Monday's review that the economic benefits of Britain's EU membership outweighed the loss of independence on policy.
However, polls suggest more Britons want to leave the EU than stay in. A YouGov poll in May said 46% would vote to leave, 35% would opt to stay in, 16% were undecided and 4% would not vote.
Cameron says his preference is for Britain to remain inside a reformed EU. Trailing slightly in most polls, it remains unclear whether he will win the next election.
He has said he will try to renegotiate Britain's membership before giving people a straight in-out vote.
Australia is not among the top ten foreign investors in Britain, but in 2011 British government statistics put the value of existing Australian investments at 11.6 billion pounds.