US outlet breaches NZ budget embargo

To cover the budget, journalists are invited to a "lock-up" run by Treasury on the condition they do not transmit information prior to an agreed 2pm NZST release time.

Treasury confirmed it is investigating the breach, first reported by news outlet BusinessDesk.

"We are extremely disappointed with this serious breach ...  the embargoed information made available to the 200-odd people who attended the event was both restricted and sensitive," Treasury deputy secretary Struan Little said.

"Once we are confident that we have established the facts, we will advise the Wall Street Journal of the consequences of their actions."

Key data in the Wall Street Journal report of the budget was then published in other outlets.

BusinessDesk reports it is the "most serious breach of budget security in many years" and is likely to come with consequences for the journalist and outlet.

The Wall Street Journal has been contacted for comment.

Mr Little said an internal review will consider future lock-up conditions "to ensure they remain fit-for-purpose".