Trinity College Dublin has plunged further down the rankings of the world's best universities.
Phil Baty, editor of Times Higher Education Rankings, said Trinity's slip in standards should send out a warning signal.
"Trinity College Dublin's decline should be cause for alarm," he said.
"When the national flagship falls, it can affect the standing of the rest of the country.
"However, at least University College Dublin and University College Cork both had strong years."
Last year, Trinity was ranked 110th in the list of the world's top seats of learning, a year after falling out of the top 100.
But in the latest Times Higher Education rankings, it has nose-dived further down to 129th place.
Over the same period, UCD has climbed from 187th place to 161st and UCC has jumped from between 301st and 350th to between 276th and 300th.
California Institute of Technology holds on to the world number one spot for the third year in a row, followed by Harvard University and Oxford, which are tied for second place.
Ranking compilers said the drop in place for Trinity was in line with an "alarming" drop in standards across Europe, as top universities in Germany, France, Switzerland, the Netherlands, Russia, Belgium and Austria all fell down the league.
"The power shift from West to East is not as dramatic this year as the US and the UK have both managed to arrest alarming falls at the national level," said Mr Baty.
"But the trend is continuing: the vast majority of continental Europe's leading institutions have slipped, while those leading the East Asian nations have for the most part risen yet again."
Last month, a separate league table, the annual QS World University Rankings, put Trinity as the 61st best university in the world, up from 67th the previous year.
UCD dropped eight places to 131st while UCC slipped outside the top 200, dropping 20 places to 210th in the same poll.
Professor Vinny Cahill, Trinity's dean of research, said the university's drop in the latest rankings should be a wake-up call for higher education in Ireland.
"Although Trinity's score in the QS World University Rankings rose to 61 in the world last month, this latest result for the university shows that we have work to do to ensure that Irish students can continue to avail of an internationally competitive higher education without the need to emigrate," he said.
"Trinity's ranking underlines the need for more sustained public investment in higher education.
"It is important for Ireland, not just for Trinity. Trinity, in partnership with Government, should work together in a co-investment arrangement to foster the renewal of Ireland's society and economy."