A government advisory body on interculturalism has expressed concern about long delays faced by immigrants at the Aliens' Registration Office in Dublin.
Mr Kensiksa Monshengwo, from the National Consultative Committee on Racism and Interculturalism, said processing delays for non-national workers and students and those with residency or refugee status were unacceptable.
"The system is overstretched. There's a need to reorganise the whole system in light of the increasing numbers of people registering," he said.
Many immigrants living in the State for more than three months are obliged to register annually with the office in Harcourt Street. They receive a passport-size registration document, known as "the green book", which they must produce if they leave and re-enter the State.
The recent growth in the numbers of non-EU immigrant workers or students has led to a threefold increase in people visiting the office in the past four years. Non-EU nationals married to Irish citizens must also register.
In 1997, staff dealt with 10,529 people, rising to 17,064 in 1999 and 26,564 last year. Staff have already dealt with more than 24,644 people this year to the end of June.