The number of migrant workers from former EU accession states in central and eastern Europe registered to work in Ireland has increased to more than 200,000 for the first time.
Most of the workers have come from Poland (116,206), followed by Lithuania (35,497), Latvia (17,988) and Slovakia (16,951).
Workers from the 10 accession states have been free to enter and work in Ireland without a work permit since May 2004.
These statistics are just an indication of migration levels into Ireland from new EU states, however. They do not show how many migrants have since returned to their home country or how many family members a worker might have with them in the country.
Monthly figures over the past two years show there has been little sign of any drop-off in the numbers applying for PPS numbers.
While around 7,000 workers a month were registering in 2004, the monthly average rose to 9,400 in 2005. The monthly average for the first four months of 2006 has been just short of 10,000.
In total 206,000 workers have arrived here in the two years since accession.
The influx of migrant workers in the past two years is expected to lead to the highest ever proportion of foreign nationals recorded in the State when the census results are collated later this year.
The last census, in 2002, recorded a population of 3.9 million, of which 6 per cent were foreign nationals. The latest census is expected to show that 10 per cent, or 400,000 people, are foreign nationals.
Some immigrant support groups estimate that most workers stay for an average of 12 to 18 months.
However, experts also suggest that as many as a third of accession country workers do not apply for a PPS number when they arrive here.
The lifting of employment restrictions on accession country workers by a growing number of EU member states may lead to a reduction in the number of workers moving here.
For the past two years Ireland, the UK and Sweden have been the only established EU members not to impose such restrictions. However, Finland, Spain, Portugal and Greece last week announced similar arrangements.
The Government has delayed making a decision on whether to allow Romanians and Bulgarians an automatic right to work here when their countries join the EU.