The federal government will back Labor's bid to have a Senate committee investigate whether leaked National Broadband Network (NBN) documents seized by federal police should remain under lock and key.
Attorney-General George Brandis said the government will support Labor's motion on Wednesday to refer the matter to the privileges committee.
Labor wants to prevent the Australian Federal Police (AFP) from using the seized documents in its investigation by claiming parliamentary privilege over them.
The documents were seized during raids on the Melbourne office of senior Labor senator Stephen Conroy and the home of his staff member during the federal election.
More were seized last week during raids at Parliament House.
Senator Conroy said what was at stake was bigger than the prime minister's legacy as a communications minister overseeing the NBN.
It was about the constitutional right of the people, through the Parliament, to hold the government to account without fear of recrimination, he said.
"This is not about the cut and thrust of politics," he told Parliament on Tuesday evening. "What this is about is the proper functioning of the Parliament and our democratic system."
The raids were an "extraordinary attack on the Parliament and its constitutional duty to hold the government of the day to account", he said.
They had been distressing for all involved but he was heartened by the support of parliamentary colleagues from all sides who had expressed concerns about the events, he said.
Senator Brandis said referring the matter to the privileges committee was the appropriate course of action.
"The issue raises not one but two important principles. As Senator Conroy has rightly said, it raises the matter of the privilege of the Senate," the Attorney-General said.
"It is not the privilege of individual senators; it is the privilege of the Senate, as Senator Conroy has rightly said. That is an ancient privilege recognised by section 49 of our Constitution"
"That is ... a high and important principle integral to the functioning of this Parliament."
Brandis said it will be left to the privileges committee to determine the facts and what course the Senate should take on the matter.
Senate president Stephen Parry said the seized documents remained in the Senate clerk's safe.
Last week prior to the resumption of Parliament, the AFP conducted a raid on Parliament House in Canberra, as part of its investigation into leaked NBN documents.
This followed an AFP raid in May on the office of Conroy and the home of one of then-Shadow Communications Minister Jason Clare's communications staffers, where the AFP seized the tranche of documents that now rest with the Senate clerk.
NBN has maintained it was well within its rights to refer the matter to the AFP.
"It is a matter for the AFP as to whether they accept the referral and pursue any matter, based on their own independent advice and judgment," an NBN spokesperson said last week.
After the second raid, Senator Conroy said NBN had claimed its documents were covered by top-secret classification.
NBN Co has claimed the documents are top secret ... as the former minister for communications and the minister who established the NBN Co, there are no documents produced inside NBN Co that would come within a bull's roar of being top secret," Conroy said.
Prime Minister Malcolm Turnbull has accused Senator Conroy of meddling in the course of justice and bullying the AFP.
"As for him trying to use political influence to stop an investigation ... he should know better," Turnbull said.