The Government is reconsidering contracts for six new charter schools signed before the election.
New Education Minister Chris Hipkins says the National-led Government signed the contracts in the weeks before the election in breach of pre-election conventions.
"This was in clear contravention of pre-election protocols that prohibit one Government committing a future Government in the run-up to an election," he said in a statement.
"I've asked for urgent advice on the status of those contracts and won't be making any further comment on the matter until I've received it."
All parties in the new Labour-led Government oppose charter schools and Mr Hipkins said anyone involved in establishing a school knew "a change of Government would mean change for them".
But ACT leader David Seymour - who was responsible for charter schools before the election - said the new schools had already been budgeted for since mid-2016.
"All of that takes time, I don't feel that the excuse frankly that he's trying to make cuts water," he said.
National's education spokeswoman, Nikki Kaye, said clarity was needed from the Government about what would happen.
"These sponsors have spent time and money securing contracts with the Crown and preparing to open these schools. They deserve better than this," she said.
Earlier this week Mr Hipkins indicated all existing charter schools would also be reviewed individually to see if they can be integrated into the rest of the education system, or whether they would be shut.