The Taoiseach has warned it would be "challenging" to adopt a Leaving Cert hybrid model again this year.
Micheál Martin said third-level institutions would not be able to provide the same number of extra college spaces as have been available in the past two years to deal with the inflation created by calculated grades.
While a number of changes have been made to help students this year, Mr Martin told the Dáil that this year's exams cannot be a "carbon copy" of last year.
"There are, therefore, challenges with the hybrid model in year three. We will all be aware that in the previous two years, the minister with responsibility for higher education, Deputy Harris, in engagement with the third-level sector, managed to squeeze many extra places two years in succession.
"The capacity of the third-level sector to provide that equivalent number of places this year may not be as high and that is to put it charitably. That creates an additional challenge. We know hybrid models can create grade inflation. There are, therefore, challenges with the hybrid model that have to be assessed. I need to put that out there," he told the Dáil.
Labour leader Alan Kelly called for a decision on the exams, saying "students out there are waiting for an answer from the Government as to whether the Leaving Certificate will go ahead as normal or there will be a hybrid Leaving Certificate."
Calling for a hybrid Leaving Certificate model, Mr Kelly said students have gone through a difficult two years and have lost much time, despite the best efforts of teachers and schools.
"I accept it cannot be a carbon copy of what happened last year. I accept there are additional difficulties. However, a move to the hybrid model is absolutely necessary. The stress these students are under at the moment is enormous," he said.