The Government has been accused of continuing to run primary and second-level schools "on the cheap" after a new OECD report ranked the Republic close to the bottom of an international league table of education spending.
The Republic comes 29th out of 30 countries when it comes to investment in each second-level student in relation to the country's wealth. Only the Slovak Republic invests less, according to the OECD figures.
The pattern is broadly similar at primary level, where the Republic continues to languish towards the bottom of the spending league table.
Overall, the Republic's total spending on education is only half that of countries such as the US and Switzerland with Ireland spending 4.4 per cent of its GDP on education, compared to an internationally recognised benchmark of about 6 per cent.
The new figures, based on spending trends up to 2003, have drawn an angry reaction from the teaching unions.
Minister for Education Mary Hanafin said they failed to reflect the dramatic increase in spending. Total education expenditure had increased from 4.9 per cent to 5.2 per cent of national income because of a 23 per cent rise in spending over the past two years, she said.
However, the 5.2 per cent figure still puts Ireland well behind other wealthy nations.
The ASTI has accused the Government of running an education system "on the cheap".
Its general secretary, John White said: "It is absolutely unacceptable that after a decade of phenomenal economic growth, we are trailing behind all OECD countries, with the exception of the Slovak Republic, when it comes to the proportion of our wealth which we spend on educating our young people."
The INTO's John Carr said 6 per cent of GDP was the minimum spending needed to support a modern education system, but the Republic had never once exceeded this "minimum benchmark" during the boom of the past decade.
Other main findings of the report include:
The Republic is in mid-division or lower in virtually all OECD tables on education spending; it ranks 17th out of 22 countries in the amount of job-related training that adult workers can expect to get during their working lives; only 11 per cent take part in job-related continuing education and training compared to more than 25 per cent in the US and Scandinavia, and Ireland is 20th out of 30 countries when it comes to the availability of computers to students.
Describing the situation as "shameful", TUI president Tim O'Meara said: "Statistics do not lie, and these latest figures reveal that Ireland is languishing deep in the 'relegation zone' of a list of OECD countries in terms of funding."
Ms Hanafin said significant advances in Ireland's performance since 2003 were not reflected in this report.
It is estimated that current expenditure per student has increased in real terms by 6 per cent at primary and 11 per cent at second level.
The OECD report is likely to spark a fresh debate about the level of education spending. While the Government is now committed to vastly increased spending at third-level , the primary and second-level sector remain underfunded compared to other successful economies such as the US, Norway and Sweden.
In recent years, much of the increased investment in education has been spent on improving or building new school accommodation after years of chronic under-investment in school buildings.