Sydney will have a second harbour rail crossing by 2024 now that Parliament has given the green light to leasing public electricity assets, the New South Wales Government has said.

Legislation to partially lease the state's power network was passed by Parliament last night.

The new harbour crossing is the centrepiece of the $20 billion infrastructure package the Government promised to build using the proceeds from the sale.

It will form part of what will be called the "Sydney Metro" — a new 30-kilometre high-capacity rail line from Bankstown through the city, which will connect to the north-west rail link via twin tunnels under the harbour.

Premier Mike Baird said there had been talk about a second harbour rail crossing for 20 years.

"The reason it didn't progress is quite simple: the funding wasn't there," he said.

"Well, what we secured last night is a green light for that funding so that the project is well and truly underway."

Transport Minister Andrew Constance said tunnel boring machines would be in the ground by 2017 and the project should be complete by 2024 at the latest.

"We want to get this done as quickly as possible," Mr Constance said.

"We are going to be engaging international experts to ensure that this is a project delivered at rocket speed.

"We are going to see, I think, a revolution in terms of public transport. This is the game changer."

He said the cost of extending the north-west rail line to Bankstown was estimated to be between $9.6 billion to $11 billion.

The promised "Sydney Metro" rail line will connect Bankstown to the north-west rail link. ( Supplied: NSW Government )

Labor, Greens warn power funds could fall short

The Opposition and Greens have both accused the Premier of overestimating how much money would be raised from the leases, and warned he would not be able to deliver on all his infrastructure promises.

Mr Baird said he was confident he could attract a good price, but even if it did not meet expectations the rail crossing would go ahead.

"We are going to build it. It is going to transform this city," Mr Baird said.

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The Government said geotechnical work for the project had already begun, and it would release more details about routes and station locations once that work was complete.

The Upper House passed the power privatisation legislation 19 votes to 17 last night after the Government secured the support of the Christian Democrats, who hold the balance of power.

Amendments to the legislation, introduced by the Christian Democrats, include five-year job guarantees for electricity workers and an independent review of an Access Economic Report, which the Government frequently quoted to argue the financial benefits of the leases.

Labor and the Greens proposed more than 20 amendments each, but all of them were defeated.

Opposition Leader Luke Foley said Labor would now drop what he called its "obsessive focus" on power privatisation.

He said it was time for Labor to move on and make sure the Premier delivered on his infrastructure promises.

"There are many other issues in state politics and under my leadership the Labor Party will not have an obsessive focus on this one issue. We won't be fighting the last war," he said.

Greens MP John Kaye said the outcome was not a win for the people.

"There isn't anything really in the way of upsides in this legislation for anybody in New South Wales other than the multinational utility operations getting control of this state's future," he said.

Meanwhile, Liberal MP Catherine Cusack shared with her Facebook followers an insight into the attendance demands on Government MPs in the divided Upper House.

A screenshot of her phone showed a string of text messages from Upper House whip Peter Phelps, demanding Government MPs' attendance in the chamber for each of the votes on the bills.