AFP raid on Labor offices 'improper'

NBN documents seized by federal police during raids on the office of a former Labor senator will be withheld from investigation after a Senate committee found it was an "improper interference" on the functions of parliament.

The Senate privileges committee has recommended the seized documents be returned to Stephen Conroy but that parliament refrain from making a finding of contempt.

"The committee considers that an improper interference has occurred on this occasion," committee chair Labor's Jacinta Collins told parliament on Tuesday.

The committee noted that information discovered during the raids may have helped identify an NBN employee alleged to have leaked information.

The documents were seized during raids on the Melbourne office of former senator Conroy and the home of his staff member during the federal election.

They have been under lock and key in the Senate clerk's safe since, after Labor claimed parliamentary privilege over them.

The privileges committee was asked last year to investigate whether the raids relating to leaked national broadband network documents improperly interfered with the duties of Senator Conroy.

It was asked to investigate whether the raids on Senator Conroy's office, his staff member's home, or the Department of Parliamentary Services improperly interfered with his duties or whether any contempts were committed.

Senator Conroy at the time described the raids as an "extraordinary attack on the parliament and its constitutional duty to hold the government of the day to account".

The Senate has adopted the recommendations of the report.