The Greens say they will support moves to split Telstra after winning a key concession from the Government on the National Broadband Network (NBN).

Draft legislation indicated the Government had wanted the power to automatically privatise the NBN after it was up and running.

But the Greens want the network kept in public hands, arguing that selling it would repeat the mistake of privatising Telstra.

The Government has now agreed to insert a clause that ensures the Parliament would have to vote on any plan to privatise.

Greens Senator Scott Ludlam says in return the party can now support legislation that forces Telstra to split its retail and wholesale arms.

"That was the last issue that was a sticking point for us," he said.

Senator Ludlam says there needed to be proper scrutiny of any future NBN sale.

"It won't be automatically privatised, it will need to be subjected to a full and comprehensive public interest test done partly by the Productivity Commission and partly through a joint parliamentary committee," he said.

"If the Government still insists on privatising it after that, it will now have to be submitted to a vote in the Parliament."

The Government still needs to win the support of crossbench senators Nick Xenophon and Steve Fielding for the bill to pass.

But Communications Minister Stephen Conroy says he has had positive signals from the senators.

"The Greens have always been largely supportive of the bill, Senator Xenophon has also been largely supportive of the bill," he said.

"He's said that many times we're in negotiations with all of the minor parties but also with Senator Fielding, he's also given some positive indications towards the bill in the last few days."

He says he is discussing ways he can give Senator Xenophon information without releasing anything that is market sensitive data or jeopardise commercial negotiations.

Yesterday, the Greens declined the offer of a private briefing on the NBN because they were being asked to sign a seven-year confidentiality clause.

The Greens, the Opposition and other crossbench MPs 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.

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