Former prime minister Malcolm Turnbull has warned the United Kingdom could be "vulnerable" if it commissioned Chinese firm Huawei for its rollout of 5G technology.
Mr Turnbull made the warning on BBC radio after UK prime minister Boris Johnson challenged critics to offer any alternatives.
The UK's National Security Council is set to make a decision on the matter within two weeks.
Mr Turnbull, who blocked Huawei from Australia's 5G network during his term as prime minister, warned: "We did a lot of work (to see) how we could mitigate the risk and the conclusion we came to was that there just wasn't a satisfactory mitigation of the risk."
He said the British could use two "very large vendors", Erickson and Nokia.
"Prudence would suggest that the better course of action is not to use high-risk vendors and 5G, there are alternatives, European alternatives," he said.
Mr Johnson said said critics of Huawei must offer an alternative provider.
He said he did not want to "prejudice" the country's ability to share intelligence with allies in the so-called Five Eyes arrangement - a collaboration between the UK, Australia, US, Canada and New Zealand - as a result of the improvements he had promised voters in his election manifesto.
The upgrade from 4G to 5G will revolutionise mobile internet capabilities, with consumers able to download a two-hour film in less than four seconds - 10 to 20 times faster than on 4G.