The Cook Islands opposition leader, Dr Terepai Maoate, says the government is unlikely to achieve its revenue projections in the budget.
He also believes that if the government carries out its spending plans, there will have to be a supplementary budget later in the year.
Dr Maoate says one of the particular concerns is the increases in the ministerial support fund.
"It's quite clear to me that the intention here is to probably satisfy ministers and ministries what are they are bidding for and most likely goes through the first part of the year anyway and come up with a supplementary and patch it up."
The budget has been presented in parliament and will be debated later this week.