The Greens have declined the offer of a private briefing on the National Broadband Network (NBN) because they were being asked to sign a seven-year confidentiality clause.

The Greens, the Opposition and other crossbench MPs have called on the Government to release the 400-page plan before Parliament rises for the year.

But the Government only offered private briefings to the Greens and independents.

Greens Senator Scott Ludlam says he was asked to sign a confidentiality clause which would bind him to secrecy for seven years.

"It imposes a seven-year non-disclosure option, which would be voided for the material that the Government eventually does put into the public domain," he said.

"The confidentiality will lapse but I have no idea how much they intend to hand over. So with great reluctance, I won't be accepting the private briefing."

Senator Ludlam says the Government's offer was not appropriate.

"I just don't think parliamentarians should be signing non-disclosure agreements in order to do their job," he said.

"I was elected by more than 100,000 Western Australians. I'm trying to do my very best in the role as a national spokesperson.

"It would have been great to be able to get the briefing but what we were asking for was for that material to be in public."