Minister for Education Ruairi Quinn has raised the possibility of using some of the resources paid out in child benefit to fund a second year of free pre-school education for children.
Fianna Fáil Education Spokesman Charlie McConalogue questioned if it were acceptable for a minister to go on national radio to start a debate about such an important issue.
Speaking on RTÉ's Morning Ireland, the minister said the move was not imminent, but he wanted to open the debate on the issue.
It was a matter of re-allocating funds, rather than raising new money, he added.
The minister said a second year of pre-school education would have a "dramatic effect" on the life chances of children from disadvantaged homes.
"We could probably get a better outcome for the future child, who becomes the adult, by ensuring that a portion of that resource, currently being expended, will be focused into a second year of pre-school education, quality education," he added.
Mr Quinn also said that €5m would improve the quality of pre-school leaders by improving their training.
Mr McConalogue said the minister did not have any accurate facts or figures, that he had not consulted colleagues or experts and he did not have any answers whatsoever about what was in store for families.
He said what he called "back of the envelope" economics would cause alarm among low-income families.