Papua New Guinea's opposition is to seek court action on its claim that the 2017 national budget is fraudulent.
The government passed the budget in parliament on Tuesday after having given the opposition a week to digest it.
However shortly before the vote, the opposition walked out of the chamber in protest after detecting inconsistencies in the figures.
When Treasurer Patrick Pruaitch presented the budget on 1 November, the overall figure given was $US4 billion.
But in this week's Appropriation Bill speech as observed by the opposition, the figure was $US6.6b.
The Opposition Leader Don Polye announced that an application would be filed for a Supreme Court interpretation of the budget.
Speaking to local media, the opposition MP Kerenga Kua said the Appropriations Bill was invalid because it was inconsistent with the budget as it had been presented.
"The speeches read and the motion put forward was about something else, and what they circulated to be the bill was something else. So to that extent, that bill is not a bill, therefore we have no bill on the floor."
Meanwhile, the Treasurer has defended the budget papers, saying the opposition misunderstood that the $US6.6b appropriations figure included $2.6b in short term public sector debt that needed to be rolled over in 2017.
Mr Pruaitch said that the 2017 national budget involved a total revenue of $US3.4b with expenditure pegged at $US4b for an overall deficit of almost $US600 million.