The Primary Principals' Network (PPN) has accused the Minister for Education of being misleading when she stated on radio this morning that the average pupil-to-teacher ratio in primary schools was 17.5 to 1.
Mr Sean Cottrell, PPN director, said Ms Hanafin was including teachers involved in administration and classes for disadvantaged or special needs pupils.
Mr Cottrell said the class average for primary school teachers under normal circumstances was 29 to 1. This figure was supported by a spokeswoman for the Department.
Speaking to ireland.com, Mr Cottrell said the admission by the Minister that the Government pledge to cut primary school class sizes to 20 by 2007 may not be met was denying children a "fundamental right".
He said: "In recent months The hospital trolley is a very visual images that has stuck in people's minds. Children in large classes being left behind don't make the same visual impact as a hospital trolley but the impact on people's lives is probably similar".
The PPN, which represents 3,300 principals in the State, today said its members were "extremely frustrated and disappointed" by the admission from the Minister.
Speaking on RTÉ radio this morning, Ms Hanafin said: "I am genuinely not sure that it is doable, given the fact we already have expansion in the system, we have a lot of retirements, we have teachers who go on job sharing or career breaks.
"There is a particular concern about unqualified teachers" she added.
"This will obviously place greater demands on resources but I will be targeting in the first instance disadvantage. We have to meet our special needs requirements."
She said smaller primary school classes needs to be worked out on a phased basis, and added that the target of ratio of 20 to 1 remained "a commitment for Government, it is an educational imperative.
"I recognise that small class sizes is to the best benefit of children throughout the system," Ms Hanafin said.
However, Mr Cottrell questioned the Minister's focusing of resources in areas of disadvantage, saying there "is little evidence to suggest that the resources being put into disadvantage are having an effect".
He said the problem was there was no consistency or equity in the allocation of resources. This was compounded by a lack of accurate data. "What we need is a proper scientific database of all primary school pupils within the country. Without a digital database it is impossible to apply resources equitably," he said.
Such databases were in place in other countries and were vital to providing the right services in the right areas. Mr Cottrell said what was needed was a system which allocated resources based on the needs of the pupils in a particular school.
Mr John Carr, general secretary of the Irish National Teachers Organisation, also questioned that a shortage of teachers was an issue.
"It is doable on a phased basis. We have anything up to 1,400 1,500 teachers coming out in a year. Overall, to have all children under nine in class sizes under 20 would take another 3,000 teachers.
"The teachers will be there if the Government is willing to commit and put the teachers into the classroom," he said.