Federal Labor is playing down suggestions the party is divided over the government's plans to spend up to $368 billion buying and building a fleet of nuclear-powered submarines.

Labor backbencher Josh Wilson used a speech in the parliament to speak out against the AUKUS pact with the United Kingdom and the United States, fearing it might undermine Australia's commitment to nuclear non-proliferation.

"I'm not yet convinced that we can adequately deal with the non-proliferation risks involved in what is a novel arrangement, by which a non-nuclear weapons state under the NPT (Non-Proliferation of Nuclear Weapons Treaty) comes to acquire weapons-grade material," he told the parliament.

None of the politicians to whom the ABC has spoken have called for AUKUS to be abandoned. They universally say while they have accepted it, they see it as their role to raise questions about the deal. 

A requirement of the AUKUS pact is that Australia must store the spent nuclear reactors after the submarines are decommissioned, beginning in the 2050s.

A Labor politician — speaking on the condition of anonymity — told the ABC they estimated up to 10 Labor politicians were continuing to raise questions or concerns about AUKUS, particularly around nuclear proliferation and waste issues. 

At a Labor partyroom meeting on Tuesday morning, three politicians raised questions about AUKUS. The questions were about funding, human capital and what it meant for Australia's defence sovereignty. 

No one in the meeting spoke against the pact nor the nuclear elements of it, a Labor politician later said.

Parts of the Labor Party have a long history of campaigning against nuclear developments in Australia and close ties with the United States are not universally supported by party branches. 

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Mr Wilson — who holds the seat of Fremantle in Western Australia — was the first to break party ranks on Monday, when he told parliament the nation must be able to have a "mature" debate about the risks of pursuing the AUKUS security pact.

"It should be a statement of the obvious to say that — with an undertaking of this scale, complexity, cost and duration — there remain considerable risks and uncertainty. That is the plain, hard reality," he said.

Mr Wilson questioned the proposed timelines for delivery of submarines, noting from the experience of building the Collins-class submarines and abandoned French subs that "building submarines inevitably takes longer and costs more than you anticipate".

He said that, while he supported the work of the government, he was not convinced the nuclear-powered submarines were the best answer for Australia.

In particular, Mr Wilson questioned plans for disposal of nuclear waste, saying Australia had not yet managed a solution to store low-level nuclear waste after 40 years, and now was taking on the challenge of safely disposing of high-level waste.

"It is a significant partnership with two of our most important and closest allies, but it will only be effective if we do our job as parliamentarians, which is to look closely and ask questions in order to guard against risk."

Former prime minister Paul Keating said there was disquiet within the party over AUKUS as he levelled his own criticisms of the party's leadership but, so far, Mr Wilson is the only sitting Labor member to question the deal.