RNZ can reveal a major concern of Treasury in opposing the Green School grant was it did not yet have the full education approvals needed for a private school.
Greens co-leader James Shaw has apologised for the decision to sign off on the $11.7 million grant, calling it an error of judgement, after a massive backlash.
The Treasury advice to Shaw and the others ministers who signed off on hundreds of projects for infrastructure investment says the Green School does not have "full private school registration" and would be unlikely to get that until mid next year.