Mr Macron said the decision to award the contract to DCNS was "an honour for French industry". He stressed that he did not want to delay the procurement of submarines any further but said Australia should "explore nuclear-powered options while our committed costs are only in the hundreds of millions". "Not more robustly challenging the nuclear no-go mindset is probably the biggest regret I have from my time as PM," Mr Abbott said. "I'm not saying that we must go nuclear but surely we should at least consider the option before the opportunity is lost for another several decades. The French-based design is hardly begun, let alone finalised. No contract to build has been signed and won't be for years. This is because it's a completely new sub – inspired by, rather [than] based on the existing nuclear model – that needs to be designed from scratch rather than simply modified to take a different engine. "The first question would be whether the US could provide us with their nuclear-powered subs. The US already provides Australia with its most advanced aircraft and tanks and its most sophisticated submarine torpedo weapons system. We have nothing to lose from starting a discussion on this issue with our allies and friends – Britain and France – as well as primarily with the US."

Tony Abbott believes he won his election on carbon pricing, rather than simply because the voters had had enough of Rudd/Gillard/Rudd. Credit:AAP Mr Abbott suggested the nuclear-powered submarines could initially be based at the US base in Guam while Australia builds up its domestic nuclear capabilities, which are currently limited to the Lucas Heights reactor in Sydney. The former prime minister pointed out that Indonesia, Singapore, India and Vietnam are expanding their submarine fleets, South Korea has 14 vessels already and Japan 19, while Russia and China's Pacific fleets dwarf Australia's and include nuclear-powered boats. "Our new subs are supposed to be "regionally superior" – including, presumably, to the sharply increasing numbers of nuclear-powered attack submarines that are based in our region," he said. "Armed with the best US combat system, they should be; but they still have to be in the right place at the right time – and a conventional sub takes at least a fortnight to go from Australia to the South China Sea, through which passes more than 50 per cent of our trade."

​"Conventional subs need to surface frequently to recharge their batteries, need to refuel every 70 days, and can only briefly maintain a top speed of about 20 knots. Nuclear-powered submarines, on the other hand, can stay submerged as long as the crew can endure, never have to refuel, and can travel at nearly 40 knots." The Turnbull government has already privately discussed converting the Shortfin Barracuda into a nuclear-powered vessel in the future, but experts have warned it could take up to 15 years to have the domestic capacity to service the vessels. Mr Abbott also suggested it may be possible to secure bipartisan support from Labor, as the opposition avoided playing politics on national security. To make that point, he added that "Labor has actually been stronger than the government on the assertion of freedom of navigation rights in the South China Sea".

Labor Defence spokesman Richard Marles last year said Australia's navy and airforce should be "fully authorised" to conduct freedom of navigation exercises in the South China Sea, including within 12 nautical miles of artificial islands built by China. Mr Abbott's speech comes just days after he delivered an alternative political manifesto designed to revive the government's political fortunes and win the next election. It also comes as the Turnbull government has been gripped by political infighting all week over same-sex marriage. Mr Pyne issued a grovelling apology on Wednesday after a leaked tape emerged in which he boasted that Coalition moderates could legalise same-sex marriage in the near future. Loading A day later, Fairfax Media revealed that moderates Senator Dean Smith and lower house MP Trent Zimmerman were drafting a private members bill to legalise same-sex marriage.