Early Childhood Ireland has said that Labour's plan to subsidise childcare will cost more than the €500m proposed.
The party has todaypromised to introduce €2-an-hour childcare if it is re-elected.
The State-subsidised scheme would apply to children aged between nine months and 12 years.
The party said that the proposal would cost the taxpayer around €500m a year.
However, Teresa Heeney of Early Childhood Ireland says the cost would be significantly higher than that, if the scheme is rolled out in every town and if childcare providers are to be paid properly.
"What we've got today is astonishing, and I'm sure parents are looking at it," she said.
"The idea of childcare being available at €2 per hour, and I'd say there's many, many of them saying: 'Finally, somebody's listening'.
"But what I would say is that €500m won't even come close to what this will cost, if they are to do this properly."
Start Strong – a group campaigning to improve Government policy on early years in Ireland, gave Labour's announcement a cautious welcome.
“Steps such as reducing childcare costs by subsidising services, and increasing funding based on staff qualifications, are large investments, but in reality Ireland, at 0.2%, is well below the OECD average (0.8%), when it comes to investing in early years," said director Ciairín de Buis.
“Such measures will go a long way to closing this gap. Linking state subsidies for childcare services to quality, placing a cap on fees to parents, regulating childminders and reforming our current inspection system, will be essential.”