The Greens have reportedly joined independent Senator Nick Xenaphon in declining a confidential briefing from the Government on the NBN business plan.
The party's ICT spokesman Scott Ludlam told ABC News yesterday that he had decided not to accept the Government's offer "with great reluctance".
The key reason behind his decision was reportedly that the briefing came with a non-disclosure term of seven years "which would be voided for the material that the Government eventually does put into the public domain," Ludlam told the ABC.
An article by The Punch had since reported that the Government had cut the non-disclosure period from seven to three years.
The Greens had led a Senate motion for the Government to produce the NBN business plan last week.
The Government did not comply, instead saying it would release the plan after parliament had finished sitting for the year.
Senators had been calling for the documents to be tabled before they were to vote on legislation that would put in place some regulatory frameworks for the operation of the National Broadband Network.
Senator Xenophon said last week he would refuse to sign a non-disclosure agreement in return for a private briefing.
However, Senator Stephen Fielding said he had agreed to a private briefing on the Government's terms.
Opposition treasury spokesman Joe Hockey told the ABC's Insiders program yesterday that he didn't buy the Government's line that it could not release the NBN business plan because parts were "commercial-in-confidence".
"We used that line in government," Hockey said.
When asked whether the previous Coalition government had gotten away with using it, Hockey replied: "Well, not always I can tell you. And nor should we have."
He suggested the Government "copy the document into another file and just press edit delete for those areas that are sensitive. And I'm sure they can get the document out pretty quickly.
"This is just a try-on," Hockey said.
"They're trying to avoid something and it looks that way and it probably is."