New uni fees only apply from 2016: Abbott

New university fee structures will only apply to students who enrol in courses from 2016 when the changes come into effect, Prime Minister Tony Abbott says.

Mr Abbott reassured students signing up for courses this year and next year their fee structure would not change mid-course.

"If you start a course under one system you'll finish it under that system," Mr Abbott told ABC radio on Wednesday.

Mr Abbott's comments came the morning after he cancelled a visit to a Geelong university citing security concerns.

Nation-wide protests are planned in response to university deregulation and higher tuition fees unveiled in the federal budget.

"If you are studying now your conditions of study won't change. If you start next year your conditions of study won't change. It's only for those who start when these changes kick-in in 2016 that will have the different conditions applying to them," Mr Abbott said.