AUKUS deal slammed as 'one of worst policy decisions'

"My regretful conclusion is that Australia's no holds barred bipartisan embrace of AUKUS Pillar One is more likely than not to prove one of the worst defence and foreign policy decisions our country has made," he told the inquiry on Thursday.

"Not only putting at risk sovereign independence, but generating more risk than reward for the very national security it promises to protect."

Having served as foreign minister from 1988 to 1996, Mr Evans said he couldn't imagine any of the governments of which he was in cabinet for more than a decade making this decision to green light the submarine deal.

Under the AUKUS deal, Australia will buy three used Virginia-class submarines from the US, before the new SSN-AUKUS boats enter service from the 2040s.

A UK House of Commons defence committee into the pact previously found "shortfalls or delays in funding" could threaten the delivery of the new fleet for Australia.

Referencing well-known submarine production issues in both the US and UK, Mr Evans said Labor must acknowledge the gravity of the risk that the nuclear-powered fleet Australia had been promised under the pact might not be delivered on time or at all.

"At the very least (the government) should now devote major resources to developing a fallback plan premised on the possibility of that failure," he said.

The crowdfunded inquiry is being overseen by former Labor minister and Midnight Oil frontman Peter Garrett.

Speaking in London following ministerial talks with UK counterparts, Foreign Minister Penny Wong said AUKUS remained critical to ensuring Australia's sovereignty.

"This is not an academic exercise or a theoretical procurement exercise," she said.

"It is the response to the central question, which is, how do we secure capability for Australia that is critical to assuring our sovereignty and ensuring peace in a much more contested region?

"That is why this government, and these governments, are so determined to deliver it."