The government is playing down three Labor MPs querying Australia's plan to acquire nuclear-powered submarines.
Fremantle MP Josh Wilson says he is not convinced whether Australia needs the new submarines and three Labor members questioned the deal in a caucus meeting on Tuesday.
Cabinet minister Don Farrell says the Labor Party has a history of democratic practices and members were free to ask questions of their leaders.
"We are a democracy in the Labor Party and people can express a point of view," he told parliament.
"There are lots of details about the AUKUS decision. I'd encourage everybody to ask questions, even the opposition."
Mr Wilson questioned the deal in parliament on Monday but noted he wasn't privy to private security briefings.
"I'm not completely convinced that nuclear-propelled submarines are the only or best answer to our strategic needs," he said.
"The AUKUS agreement, arrived at with some characteristically questionable secrecy by the former government ... is not a sports team of which we have all suddenly become life members."
Mr Wilson also questioned how nuclear fuel would be disposed of, noting the UK and US had struggled to deal with their decommissioned boats properly.
Three Labor MPs asked Prime Minister Anthony Albanese questions about the deal at a caucus meeting in Canberra on Tuesday.
Michelle Ananda-Rajah was one of those MPs and has since come out saying, "I fully support the government's AUKUS plan".
Media reports suggest the second MP was Libby Coker.
The questions related to workforce issues, cost and how Australia would retain its sovereignty. They included concerns from constituents.
Opposition defence spokesman Andrew Hastie said the prime minister needed to unite his caucus if he wanted to succeed in uniting the nation behind AUKUS.
"It's clear now that on the left flank of the Labor Party, they have great reservations about AUKUS," he said.
He said the queries were "undermining the government's position".
But Mr Hastie wouldn't comment on whether any coalition MPs had expressed reservations about the deal.
"Our adversaries are seeking to undermine this very deal. It's right that we ask questions but we need to be unified around this," he said.
A Labor branch in the Sydney suburb of Petersham, which sits within the prime minister's electorate, passed a resolution against AUKUS and called for Australia to withdraw from the pact with the US and UK.
The resolution said the agreement would threaten Australian sovereignty - which the government denies - and goes against Labor's traditional opposition to nuclear power.
It also branded the decision "an obscene waste of money".
The Labor branch in Port Kembla, which is being considered as a future submarine port, also passed a resolution against the hosting of nuclear vessels in the Illawarra region on the NSW coast.
Two unions have also come out against the deal.
The maritime union's southern NSW branch secretary Mick Cross said the basing of nuclear submarines would put at risk the expansion of shipping arising from renewable energy investment in the area.
The Electrical Trades Union has described it as a "betrayal of responsibility to Australia's non-nuclear policy", labelling nuclear technology as "inherently dangerous".
Mr Albanese last week said in an interview the caucus had been "taken through this process" and he hadn't heard any opposition from within his party.
