The Government has censored around 90 percent of a data retention consultation paper that was released this week under Australian Freedom of Information laws.
They were distributed by the Attorney-General's Department (AGD) to internet service providers (ISP) at a telecommunications industry briefing in March.
"As the matters are not settled and proposed recommendations may not necessarily be adopted, release of such documents would not make a valuable contribution to public debate," wrote AGD legal officer Claudia Hernandez.
"Rather, I consider that release of such documents may lead to premature unnecessary debate and could potentially prejudice and impede government decision making."
Greens Senator Scott Ludlam criticised the AGD's decision, arguing that the Government should allow an "open discussion in the development of the best possible policy regime".
"This excuse is extraordinary," he said. "Why is the Department making such an effort to keep this information hidden?"
The proposal is under investigation in a Senate Inquiry into online privacy that involves Ludlam, is chaired by Liberals Senator Mary Jo Fisher, and will report on its findings by 20 October.