More than $20 million from National's asset sales programme has been used to subsidise 10-year passports, which were unveiled last year to replace five-year passports.
That's despite promises from ministers the proceeds from the partial sales of Meridian, Genesis, Mighty River and Air New Zealand would go to schools, health, and transport.
The shift to 10-year passports was a popular move but it came with a price tag of around $450 each, compared with $135 for a five-year equivalent.
The solution for Internal Affairs Minister Peter Dunne: using asset sales proceeds to subsidise the rollout.
Around $23 million from the asset sales proceeds fund -- dubbed The Future Investment Fund -- was diverted to what is called the 'Passports Memorandum Account', which allowed 10-year passports to be give a $185 price tag.
"The important issue in my mind was to get the 10-year passport introduced and to get it introduced at a cost that was affordable for all New Zealanders," Mr Dunne says.
"It's been an extraordinary success, there's been a massive uptake, and I think most Kiwis would say 'well done'.
"Treasury was at one stage recommending a cost of around $450 per passport which would have been absurd, astronomical and unacceptable."
It's infuriated New Zealand First leader Winston Peters, who says National has broken its promise to spend the proceeds on schools, health and transport.
"Billions of dollars, taken under people's noses, to a cause which they were asked in 2011 to vote to partially sell these state assets, and 'don't worry about it, the money's going on these things'. And they never kept their word.
"There's something going on in American politics, and we're starting to see it here too. The system is beginning to be seen as rotten."
He says National's used the proceeds as a slush fund -- a slush fund that's now run dry.