The two biggest spending government departments, Health and Social Development, are reviewing all their spending in an effort to find cuts for next year's Budget.
However other government agencies are not required to do line-by-line reviews, even though a number failed to come up with savings this year.
Finance Minister Bill English says although not all departments have been directed to carry out line-by-line reviews, they will have to make do with the same or less money in the next three to five years.
He says while the spending restraint is real the Government is demanding that as far as possible departments don't cut services.
Labour Party finance spokesperson David Cunliffe says cuts to services are inevitable and the Government has got its priorities wrong.
For instance, he says, the amended emissions trading legislation will add billions of dollars to Government debt as taxpayers subsidise heavy polluters.