The National Party is branding the government's fees-free policy as a waste of money, following a student survey at the University of Canterbury.
A survey of more than 1000 students by the university shows that 5.8 percent of students would not have been at university had the policy not existed.
One third of the students surveyed said they were influenced by the policy but those students were more likely to drop out and did not achieve academically.
National spokesperson for tertiary education Shane Reti said his party have estimated the scheme will cost $2.8 billion over four years.
"Is $2.8 billion and a return of six percent of students, coming to university is that good value to money? My response to that would be no," he said.
However, Mr Reti would not confirm if the National Party would scrap the policy if brought into power.
"We will come up with a discussion document at the end of this year and we will have a response to free fees at that time," he said.
But Education Minister Chris Hipkins rejected those comments.
He said the scheme costs half of what National claimed and the scheme was benefiting not just those who wouldn't have otherwise studied.
"We have got more than 25,000 people now who didn't borrow for fees last year, who would have otherwise borrowed for fees, so they have lower student loan debt," he said.
New Zealand Union of Students' Associations argued the University of Canterbury's research on the government's zero fees scheme, failed to represent all students.
President James Ranstead said the results are only from the one university.
"I do believe the results would have been significantly different if the likes of Waikato University or AUT, which is clearly more diverse was surveyed.
"In fact we have found reports from the new Waikato University Tauranga campus, that a significant number of those students were really driven to study as a result of this," he said.
Mr Ranstead said there are also polytechs and industry training organisations to be considered.