France's ambassador to Australia, Jean-Pierre Thebault, said on Wednesday that Australia acted with deceit when it abruptly cancelled a multi-billion dollar deal with Paris to build a fleet of submarines.
"The deceit was intentional," Thebault told media in Canberra on Wednesday.
"And because there was far more at stake than providing submarines, because it was a common agreement on sovereignty, sealed with the transmission of highly classified data, the way it was handled was a stab in the back."
Australia in September cancelled a deal with France's Naval Group, opting instead opting to build at least 12 nuclear-powered submarines in a deal with the United States and Britain.
The new alliance, dubbed AUKUS, is designed to give Australia access to nuclear-powered submarines for the first time.
The decision has caused a major bilateral rift, with France recalling its ambassadors from Australia and the United States in protest. Thebault returned to Canberra last month, and the speech on Wednesday is the first time he has spoken publicly on the bilateral relationship.
"These are not things which are done between partners - even less between friends," Thebault said.
French President Emmanuel Macron on Sunday said Australian Prime Minister Scott Morrison had lied to him about Canberra's intentions.
Morrison has denied the claim. He said he had previously explained to Macron that conventional submarines would no longer meet Australia's needs.
Morrison and Macron spoke last week before the Australian leader publicly sought a handsake with his French counterpart at the G20 meeting.
On Friday, US President Joe Biden said the handling of the new pact had been clumsy, adding that he had thought France had been informed of the contract cancellation before the new pact was announced.