The comments come after the University of Otago council this week voted to raise domestic fees on all but one course by the maximum allowable 4%. One course was raised by 4.35%, as it was not subject to the limit.
Vice-chancellor Prof Harlene Hayne said rising costs meant it was a question of either cutting the quality of services or raising fees.
Chief operating officer John Patrick said the "indication" was that all universities would raise fees by 4%.
Mr Robertson said increases of 4% would continue under National as it continued to "starve the tertiary education sector of funding".
"National is budgeting for a decrease in spending on tertiary education over the next four years. Sadly, Steven Joyce sees education as a cost to be cut, rather than an investment in our future," he said.
In contrast to this, Labour's policy was to make tertiary education more affordable through a combination of funding for institutions and more access to student support, he said.
Green Party tertiary education spokesman David Clendon said it was "no surprise" to see fees increase, given National dumped the previous "fee maxima" policy in 2010.
"The Government gave them the message ... [fee rises are] acceptable and that's been followed by tertiary providers around the country."
The Green Party's policy was to cap fees and then progressively reduce them.
Tertiary Education Minister Steven Joyce said Labour and the Greens' approach was "typically irresponsible".
"They think money grows on trees and are always happy to hand out more and more taxpayer funding, oblivious to the impact on public debt," he said.
"The Government has increased our investment in New Zealand's universities by 13.5% over the past four years, despite the global financial crisis, tough economic times and the costs associated with the Canterbury earthquakes.
"Universities need to be focused on what they can do to keep costs down for students and that includes taking a close look at their own operating costs, just like the rest of the world is doing."
