The NSW government and opposition are required by law to submit their proposals for independent costing.
But Treasurer Daniel Mookhey on Monday said he would seek to have One Nation additionally required to submit its platform to the Parliamentary Budget Office for review.
That office would then create a budget impact statement for all three parties before voters head to the polls.
The change was recognition the three parties would credibly compete to form government, Labor said, and the office would be additionally resourced to cope with the added demand.
Premier Chris Minns said the financial exercise kept parties accountable to voters, especially when household budgets were being squeezed.
"One of the reasons why the (budget office) has been solidified into our politics, both federally and at the state level, is so governments, oppositions, political parties can't pull one over the public," he told reporters.
"They can't say one thing before the election and another thing after."
The office has only been used by the two major parties since it was established in NSW in 2010.
One Nation has had access to the federal equivalent but not used the resource and has faced frequent criticism from political opponents about putting forward policies with no price tags attached.
The party's state leader, Mike Newman, came out swinging, labelling Labor governments "Australia's worst economic managers" and challenging the party to reveal the cost of rolling out renewable energy in NSW.
The son of the former Australian Stock Exchange chairman trumpeted his credentials as a financial analyst and said budgets for several metro and light rail projects had blown out by several billions under Labor.
"One Nation will not be lectured ... Labor wants to put our policies under the microscope while leaving the full cost of its own agenda unanswered," he said.
"The public won't be conned by a political stitch-up dressed as financial scrutiny."
Former deputy prime minister Barnaby Joyce, now One Nation's deputy head, was also unconvinced of the benefits of the Parliamentary Budget Office.
"If you want to use them, knock yourself out," he told News 24, adding his team of economic advisors were more reliable.
When pressed in September on how the party would cost a controversial policy to allow people access to part of their superannuation early, Mr Joyce replied: "I'm (One Nation's) treasury spokesperson, not Jesus Christ."
Flinders University academic Josh Sunman said he understood Labor making the calculated move to force One Nation's hand, but he was sceptical about how it would translate to voters on the ground.
"A lot of One Nation supporters aren't really looking to the nitty-gritty detail," he told AAP.
"They're just angry and upset with the way things have been done by the two major parties and are looking for some other alternative.
"Strategically, it also makes sense for One Nation not to really engage with it."
One Nation intends to stand candidates for all 93 lower house seats at the March state election and it continues to perform well in NSW and federal polls.
Despite currently having no sitting MPs in the state's lower house, DemosAU's end-of-August survey of 1028 residents had One Nation running third on primary vote intention (23 per cent), behind the coalition (25) and the Labor government (32).
The government will need the opposition's help to pass the changes through the upper house, where it does not have a majority, although the coalition has indicated it will likely support the shift.
The Greens said they would not support the plan, arguing it gave One Nation undue credibility and legitimacy.
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