The Consumers' Association of Ireland says it has been inundated with complaints in the past week from concerned parents who have used the school book online retailer schoolbooks.ie.
Many parents are saying they have not received books they ordered, in some cases months ago.
They are also complaining that they are having trouble contacting the company.
The website, which is one of Ireland's largest online suppliers of schoolbooks, has so far not made any public comment on the situation.
The Chief Executive of the Consumers' Association of Ireland, Dermot Jewell, says the company needs to explain itself.
"We did try (to contact them) and similarly to many consumers it was without success. I acknowledge that anything can happen and it's possible there's a logical reason for this but those within schoolbooks.ie at this stage must know that many people are trying to contact them.
"The inability to get any response from them whatsoever is a matter for concern."