The government says an independent body that would assess the true cost of election promises would be good for democracy.
Cabinet wants the Parliamentary Budget Office to be operating by mid-2021 but needs the support of other parties.
Finance Minister Grant Robertson told Mike Hosking it would be like the Ombudsman, which is the highest level of independence you can get.
He says it's about voters having the opportunity to know parties' promises have been independently costed.
Robertson says the government needs a committee of cross-party MPs to agree to it.
"I hope everybody takes a deep breath here and the National party members of the committee get a chance to asses this reasonably."
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