The independent Parliamentary Budget Office (PBO) has released figures showing the cost of Labor's state election policies would set New South Wales up for bigger surpluses over the forward estimates than the Government's.

But the Government has warned that even if the Opposition's figures add up on paper, Labor cannot be trusted to manage the budget.

It is the first time in Australian political history that an Opposition has put its costings through an independent PBO.

The PBO report found that both sides' promises would lead to positive budget results, but Labor's net operating result would be almost $1.4 billion better over the course of the term.

Opposition Leader Luke Foley said the figures show the Government has been running an unjustified scare campaign about his party's costings.

"There'll be a series of very strong budget services under a Labor government," he said.

"You don't have to take it from me, you can take it from the independent Parliamentary Budget Office.

"Labor's policies [will result in a] costed, funded, affordable budget, keeping the budget strong, keeping the state's triple A credit rating."

But NSW Treasurer Andrew Constance said voters should not take any comfort from Labor's figures, after 16 years of economic mismanagement when it was in government.

"Even Labor can deliver a surplus by increasing tax and cancelling projects," he said.

"He may have submitted some numbers [and they] may or might not add up. But Luke Foley's credibility just simply doesn't add up."

The costings also revealed Labor would save money by reducing the amount of ministers on the frontbench and senior executives by 330 positions.

Mr Foley was unapologetic about the move.

"We'll take an axe to fat cats, rather than frontline services," Mr Foley said.

"I'm about leaner government. Five fewer ministers, less white cars, less ministerial staff.

"I don't think some of the ministers in this government are carrying a full load."

The Government, meanwhile, said it would find savings by extending the 1.5 per cent efficiency dividend it places on government departments for another term.

But Mr Constance said it would not mean fewer nurses or teachers.

"It's about cutting out waste," Mr Constance said.

"I would importantly note that these measures will protect vital frontline services, particularly in health, education and emergency services."

The PBO figures do not take into account the Government's plan to sell off the electricity network or cost any promises made beyond the forward estimates.

That means, they factor in dividends from the poles and wires which the Government would not receive if it sold them off.

But Mr Constance said other economic benefits of the sale would more than make up for the lost revenue.

"With the increased jobs you will see increased payroll tax, you will see increased stamp duties because of the housing uplift associated with the infrastructure development and growth ... and at the same time we're going to grow the economy," Mr Constance said.