An attempt by Premier Mike Baird's office to influence an investment bank's report on the government's electricity privatisation proposal is set to be investigated by a parliamentary inquiry.

Labor says it will join with the Shooters and Fishers Party to push for an upper house inquiry, which would see Mr Baird's staff and senior executives from investment bank UBS called to give evidence under oath.

The push is supported by the Greens, making it likely there would be sufficient support in the Legislative Council.

In a statement on Friday, shadow Treasurer Michael Daley and Shooters and Fishers MP Robert Borsak said they would put forward a motion "immediately upon the resumption of parliament".

"Both Labor and the Shooters and Fishers Party are concerned by the fact that Mike Baird and [Treasurer] Andrew Constance have refused to answer questions on this matter over the past three days," it says.

"There is a multiplicity of unanswered questions and it now seems the only way to get the truth from the Premier and the Treasurer is through an inquiry led by the Upper House."

Greens MP John Kaye pledged his party's support. "Just as we supported the 2011 Upper House inquiry into Labor's botched power privatisation, we will support this one," he said.

On Wednesday, Mr Baird admitted his office called UBS - one of two banks hired by the government to handle the proposed privatisation - after one of its analysts issued advice that the transaction would be "bad for the budget".

The analyst reissued the advice, removing the phrase "bad for the budget" and adding a more favourable view on the economic benefits of the privatisation.

The government and the bank insist the decision was made independently but Mr Baird has refused to give more details.

Mr Baird has said if the government is re-elected he will privatise all of electricity transmission firm Transgrid and 50.4 per cent of distributors Ausgrid and Endeavour Energy via a 99-year lease.

Labor opposes the privatisation due to the loss of dividends and other payments to the state budget and is claiming electricity prices will rise.

On Friday former Labor Treasurer Michael Costa accused opposition leader Luke Foley of telling "desperate lies" despite telling parliament in 2008: "It is the wrong policy to privatise a regulated monopoly in the form of transmission and distribution".

But Mr Foley said while some "elite opinion" favoured electricity privatisation, "I'm with the great mass of the people of NSW, who own our electricity network and do not want it sold".

2015 NSW election: Policy reckoner

<a href="http://smh.com.au/interactive/2015/nsw-election/policy-reckoner/app.html" _rte_href="http://smh.com.au/interactive/2015/nsw-election/policy-reckoner/app.html">2015 NSW state elections - policy reckoner</a>