Revenue Minister Peter Dunne says he will vote against legislation establishing charter schools.
However, the Government still looks to have the numbers, with the Maori Party giving support at the Bill's second reading.
The education and science select committee reported back to Parliament last week on the Education Amendment Bill and it is due to have its second reading in Parliament later this month.
Associate Education Minister and ACT party leader John Banks wants the first schools up and running next year.
Dunne says he's not convinced by the charter schools model and he is particularly concerned at proposals which will allow charter schools to employ teachers who are not registered or nationally certified.
The United Future leader is also worried the schools will not be compelled to follow the National curriculum.
"The current system already provides for a significant range of schooling opportunities, and I cannot see there is a need to introduce the partnership schools approach to achieve the level of flexibility the proponents of partnership schools are seeking," he said.
The select committee recommended that charter schools be subject to investigation by the Ombudsman.
The independent schools will receive the same per-child funding from the Government but are less-tied to Education Ministry regulations.