The president of UCD, Dr Art Cosgrove, has said there could be major difficulties implementing any new college fees scheme.
Dr Cosgrove said the "fundamental problem" was not the principle of getting the better off to pay, but implementing a scheme that would not create major anomalies.
"Since it is widely recognised that the State cannot accurately measure the income of many of its citizens, any system of exemption based on parental means must be flawed," he said.
"The inequities to which it gives rise provide the main argument against the reimposition of fees," he said.
Speaking at a conferring ceremony yesterday, he said that whatever Government proposals eventually emerged should not damage the quality of education provided by universities.
"What now seems clear is that the State will be unable to afford, on its own, the cost of maintaining a university system that is internationally competitive. If the shortfall is not to be met by the reimposition of fees, where will it come from?" he asked.
"Other countries face a similar dilemma and have implemented or are considering loan systems, graduate taxes or other mechanisms to supplement the State's contribution. What will Ireland do? Whatever is decided, the quality of our universities must be maintained. No one will benefit if standards are allowed to fall," he said.
Meanwhile a report has found that poorer students at third level have to engage in alarming levels of borrowing to fund their education.
Poorer students do not have to pay fees, but funding their living expenses is a major problem, the report claims. It says regardless of what happens on fees, the inadequate support for poorer students will remain a major obstacle in widening access.
The report, published by Institute of Public Administration of Ireland, points out that fees are not the only issue that needs to be addressed at third level. It says borrowing by poorer or "access" students is also posing problems.
"The percentage of access students engaging in borrowing also serves as a worrying aspect of this survey's findings. With almost half the respondents engaged in borrowing, concern has to be expressed for the long-term consequence of this action," it says.
The report, written by Mr Micheál Collins, of Trinity College, and Mr David McGuire, of the University of Limerick, who surveyed 266 disadvantaged students in four colleges, found that borrowing occurred because State funding was inadequate.
"Engaging in borrowing and or part-time employment seems to have been a necessary response. Even allowing for those who wish to sustain some labour market connections, the average number of hours worked by access participants seems high at 16 hours per week," it says.
The report notes that student funding is not available during the summer months. It says this affects mature students in particular.
Why invest resources in assisting students for three-quarters of the year, only to abandon them for the other quarter, it asks. "While it is important not to discourage short-term employment opportunities, summer time instability seems unnecessary and avoidable," it says.