The Government's lynchpin election promise of a National Broadband Network (NBN) has inched closer to fruition today, after a deal was struck with independent Senator Nick Xenophon.

Senator Xenophon had been refusing to back NBN legislation which would enable the separation of Telstra's wholesale and retail arms.

He wanted the NBN business case released before promising his vote in the Upper House on the bill to separate Telstra.

The Government has now confirmed it has agreed to release a summary of the business plan ahead of a vote in the Senate.

The Government only has until the end of tomorrow to get the bill passed this year before Parliament rises for the summer break.

Senator Xenophon has also secured a briefing from NBN Co head Mike Quigley, and a joint parliamentary committee to oversee the network's rollout.

The Government also has Greens support for the bill but still needs the backing of another independent senator, Steve Fielding, who is yet to make a final decision.

Prime Minister Julia Gillard says a 50-page summary of the business plan will be released later today.

Ms Gillard says the summary will not include any information that would cause market uncertainty.

But she says the summary will show the total cost of the network is now expected at $35.7 billion instead of the $43 billion first thought.

"That difference is overwhelmingly explained by the agreement with Telstra and the ability therefore to get access to Telstra infrastructure for the rollout," she said.

"I have determined to do this in consultation and joint work with the minister (Stephen Conroy) after a series of detailed discussions with the independent senators," she said.

"We are continuing to engage closely with the crossbench members of the House of Representatives who supported the NBN and supported this bill.

"We've determined, following those discussions, that it is possible to publicly release carefully selected materials which answer some of their key questions."

The Government has spent much of the past fortnight battling the Opposition and crossbench MPs, who were demanding the release of the NBN's business case before they were forced to vote on the Telstra bill.

Senator Xenophon has thanked the Prime Minister for agreeing to release the summary of the plan.

"This is a win for transparency," he said.

"I'm very grateful to the Prime Minister for getting involved in this process."