Students have blamed financial pressures and a lack of career guidance for the high dropout rate on many university courses.
USI, the Union of Students in Ireland, said the rates at some universities were "a matter of great concern" and it was a "national scandal" so much talent, resources and energy were being wasted.
The USI president, Mr Julian de Spainn, said he was shocked by the high dropout rates - reported by The Irish Times yesterday - in some colleges.
"The research in this area shows there are two main reasons for this attrition - financial difficulties and unhappiness with the course of study."
He called for a major increase in career guidance at second level schools so students were able to make informed choices. Mr Colm Jordan, USI's education officer, said: "The disgraceful situation at present in relation to guidance counselling provision at second level is also a prime case of non-completion.
"Even though Fianna Fail promised in its most recent election manifesto to restore the ratio of one guidance counsellor to every 250 students, it has failed to honour this commitment and the current ratio is 1:500.
"The lack of progress on this issue is highlighted by the fact that there are now 730 courses being provided in 44 institutions within the CAO system. This is in stark contrast to the situation in 1982 when there were only 95 courses on offer in nine institutions." He said rates of career guidance at third level were not much better.
Mr de Spainn said the poor level of grants was forcing many students to abandon their plans for college or to drop out in the first year. He said the rate of £49 a week was ludicrously low.
"In relation to financial difficulties, a report by Prof Pat Carey last year on those who turn down CAO offers found that 12 per cent of those who turned down a place did so for financial reasons." USI said the dropout rates for computers and science were particularly bad. Mr Jordan said the maths curriculum at second level could be one reason. The curriculum needed to move away from "highly mechanical maths" and move towards problem-solving which was valued on high-tech courses.
The issues of college dropouts and financial support at third level are expected to be debated at USI's annual conference, which runs from March 19th to 23rd in Ennis, Co Clare.