A South African official is describing the country's protest-hit universities as inefficient, saying the student body of one million includes several hundred thousand who are performing poorly and languishing in the system.

Statistician-General Pali Lehohla's comments on Tuesday about universities that receive some state funding follow student demonstrations for free education that have swept many campuses in recent weeks.

Lehohla says the university system should have 600,000 students at most. But he says many more students are "treadmilling" and failing to graduate on time.

Lehohla attributes the state of limbo largely to the fact that those students don't have the financial means to study well.

The statistician-general says free university education is impossible but recommends an education levy on graduates to alleviate the problem.