Australia’s nuclear-powered submarines will need the supervision of the US Navy to operate and maintain, threatening the nation’s foreign policy independence.

Former prime minister Malcolm Turnbull has doubled down on his criticism of the pending submarine deal in a letter to the Quarterly Essay.

A decision is expected in March on whether Australia uses the US or UK model of nuclear-powered submarine to replace the ageing Collins-class fleet, under the AUKUS security agreement.

It is widely expected the US Virginia-class model will be adopted.

Two members of the US armed services committee – Democratic Senator Jack Reed and Republican Senator James Inhofe – wrote to President Joe Biden late last year imploring him to not let the AUKUS security pact come at a cost to US capability.

They argued selling subs to Australia could stress the US submarine industrial base “to the breaking point”.

Defence Minister Richard Marles said at the weekend the US and the UK were committed to making sure Australia didn’t have a capability gap.

Mr Turnbull tweeted on Monday while the AUKUS agreement was a “worthwhile and natural enhancement of already intimate security and intelligence relationships”, the submarine element of the agreement “delays vital capabilities and diminishes Australian sovereignty”.

“Almost completely overlooked in Australia is the fact that nuclear powered submarines to be acquired from the US will not be able to be operated or maintained without the supervision of the US Navy,” he wrote.

In his letter to the Quarterly Essay he wrote Australia needed to have a “thoroughly independent foreign policy”.

“As far as the defence of Australia is concerned, we must be able to defend ourselves and that means that all of our defence capabilities must be sovereign Australian ones, able to be maintained, sustained and deployed by Australia without the approval or supervision of any other nation,” Mr Turnbull said.

He argued the best option would be to acquire nuclear-powered submarines from France, which had a deal with Australia for conventionally powered boats but it was torn up under Scott Morrison.

– AAP