AFP officers remained tight-lipped after executing search warrants on Department of Parliamentary Services offices in pursuit of leaked internal documents relating to cost blowouts and technical delays within the national broadband network - some of which had been reported exclusively by Fairfax Media.

AFP officers began the extraordinary action from 10am but acknowledged that with parliamentary privilege being asserted, documents obtained would be treated as confidential and remain off-limits to investigators until such time as the Senate itself rules on whether privilege attaches to any documents.

The focus of AFP investigators was understood to be the DPS servers, which provide internet access to all publicly employed occupants on Capital Hill - including MPs and their staff.

"All material seized during this warrant will be handled in accordance with the provisions and guidelines relating to Parliamentary Privilege," the AFP said.

But the opposition wasted no time in again tagging the exercise as political.

"Well, what we've seen here is an effort by the NBN Co to hide the embarrassment that Malcolm Turnbull faces with a $56 billion cost; that's a $15 billion blowout in the cost of Malcolm Turnbull's national broadband network," Senator Stephen Conroy told the ABC's AM program.

Opposition Leader Bill Shorten later rounded on the government during an appearance at the National Press Club, declaring there seemed no lengths to which the government would not go to hide its embarrassment at the failure of NBN Co to meet promised performance and completion benchmarks.

In contrast, Prime Minister Mr Turnbull slammed the opposition, arguing the Coalition had rescued the NBN project from failure and was "very proud" of what it had achieved.

The warrant, which also names several media companies, including Fairfax Media, grants police access to computers, storage devices, emails, diaries, notes, internet logs and correspondence.

Mr Turnbull said it was "very important to remember that the Australian Federal Police act independently of government".

"I've been very disappointed, not for the first time, to hear Senator Conroy this morning attack the integrity of the Australian Federal Police," he said.

Mr Turnbull said he learnt of the raids on Wednesday morning from Justice Minister Michael Keenan. He said Mr Keenan was notified of the action on Tuesday night.

A spokeswoman for NBN Co. said the organisation was "completely within its rights to refer theft or other criminal matters to the police".

"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," the spokeswoman said.

Shadow attorney-general Mark Dreyfus said the leaks included information Mr Turnbull did not want to be made public because it was embarrassing for the government.

Senator Conroy's office and the home of a staff member were sensationally raided during the federal election campaign as part of the investigation into leaks of confidential information and documents from NBN Co, which Labor said show significant delays and cost blowouts under the Coalition.

Labor was contacted by the AFP on Tuesday and asked for clarification about the issues. On Wednesday morning, staff for Senator Conroy were asked to meet AFP officers at Parliament House.

"Parliamentary privilege is a law of Australia and the federal police are fully aware that I have claimed parliamentary privilege over all of the correspondence between myself, staff, staff of other shadow ministers in the course of our duties," Senator Conroy said.

"Our obligation to the people of Australia is to expose waste and mismanagement by the government and what we are seeing here is an attempt to intimidate people to not actually do their parliamentary duties."

Senator Conroy said documents held by the Clerk of the Senate would be subject to a vote over privilege protections.

"Malcolm Turnbull once made his name protecting whistleblowers, where now he is setting the police on them," he said.