National says you should have to pass to maintain your free year of tertiary education.

A third of tertiary students who took up the Government's flagship fees-free policy failed or withdrew from at least one of their courses last year, Ministry of Education data shows.

The Tertiary Education Commission (TEC) did not have details on how much the Government had spent on courses students failed or withdrew from.

But based on the 13,770 students who failed to complete at least one course, and the average course cost of $2800 for Student Achievement Component, the figure could be as high as $40 million.

Further information from the TEC showed that fees-free students tended to be younger, more likely to be NZ European, and more engaged in university-level study than non-fees-free students.

The Ministry of Education released the failure and withdrawal numbers to the Herald on Sunday after a request under the Official Information Act.

National Party tertiary education spokesman Shane Reti told Andrew Dickens points to systems like Bursaries and Scholarships, which require a B-average to hang on to.

"So the concept of the state funding all of your tuition and therefore you needing to meet some performance metric is quite reasonable."

Reti says fees-free students may not care as much about passing because they have less skin in the game.