The number of primary school students being taught in classes of 30 or more has increased by over 5,000 in the past two years, to 111,758, and just under 15 per cent of students go to school each day in classes of less than 20, according to the latest Department of Education statistics.
Despite Government commitments to reduce primary class sizes, over 111,000 - or more than one in four - of the State's 442,000 primary school students are in classes of 30 or more. A further three out of five are being taught in classes of 20 to 29, while 287 students are in classes of 40 or more.
The county-by-county breakdown of class sizes is contained in a recent written Dáil reply from Minister for Education Mary Hanafin to Labour Party education spokeswoman Jan O'Sullivan TD.
It reveals that Ms Hanafin's own constituency of Dún Laoghaire- Rathdown, as well as Wicklow and Dublin Fingal, are the worst areas in the country for large class sizes.
More than one in three primary students in these areas go to school every day in classes of 30 or over.
Other areas such as Louth, Meath, Kildare and Cork County also have significant percentages of primary students in classes of 30 or more.
By comparison, children in more rural areas such as Leitrim, Longford, Mayo, Roscommon and Tipperary North Riding are far more likely to be in classes of one to 29.
According to the figures, 287 children in schools in Clare, Cork County, Dún Laoghaire-Rathdown, Galway County, Roscommon and Tipperary North Riding are also going to school every day in classes of 40 or more.
In the 2002 Programme for Government, Fianna Fáil and the Progressive Democrats said they would reach class size targets of fewer than 20 for all children under nine by next year.
However, Ms Hanafin has since acknowledged that these targets would not be met. These are the latest figures available and relate to the current school year. Department of Education statistics for the 2003/2004 school year showed there were 106,549 students in classes of 30 or more.
In her Dáil reply, Ms Hanafin said the average class size was 24, and she suggested that class sizes of more than 29 in a school could often be due to a decision taken at local level to use teaching resources to have smaller numbers in other classes.
"Next September there will be no less than 4,000 extra teachers in our primary schools, compared with 2002," she said.
Irish National Teachers' Organisation (INTO) general secretary John Carr warned that the primary teachers' union intended to make class sizes an "election issue".