Zimbabweans travelling to the Republic need a visa under new measures introduced by the Department of Justice.
The move mirrors the UK's decision to impose visa requirements for citizens of the suspended Commonwealth country after an upsurge in numbers arriving there seeking asylum.
The UK announced the visa requirement on November 8th, bringing it into line with many other EU countries. While the Minister for Justice, Mr McDowell, decided to take a similar step on the same date, this was not publicly announced.
The visa regime was imposed in the UK because of "very significant abuse" of UK immigration controls.
As the Republic shares a Common Travel Area with the UK, it is understood the Department was concerned that failure to impose a similar visa requirement here could lead to an increase in both asylum-seekers and economic migrants from Zimbabwe arriving in Ireland from there.
There were also concerns that the UK visa requirement could lead to an increase in Zimbabweans arriving in Ireland in an attempt to enter the UK illegally.
However, the Irish Refugee Council and the United Nations High Commission for Refugees (UNHCR) in Dublin last night expressed concerns that the measure would make it harder for Zimbabwean refugees to avail of their right to seek protection in Ireland from persecution.
Ms Pia Prutz Phiri from the UNHCR said she had general concerns when visas were imposed across Europe on nationals coming from areas of conflict. "These kinds of measures, combined with carrier sanctions and other immigration controls, do tend to prevent asylum-seekers from reaching safety from conflict or persecution," she said.
Mr Peter O'Mahony from the Irish Refugee Council said a "striking number" of Zimbabweans recently coming to Ireland qualified for refugee status on grounds they had fled persecution.
"The impact of this is likely to make it more difficult for others in the exact same situation to get here and we would be disturbed by that development," he added.
Justice officials point out that there are no direct flights between Zimbabwe and Ireland and that refugee applicants could apply for asylum in the first European country they entered.
Mr O'Mahony said many Zimbabweans may feel an affiliation to Ireland as it is English-speaking. The influence of Irish missionaries on Zimbabweans might also influence their decision to seek refuge in Ireland, he added.
People recognised as refugees fleeing persecution are entitled to live and work permanently in the State. Zimbabweans accounted for 346 asylum applications out of a total of 10,508 this year until the end of last month. This compares to 102 last year and 25 in 2000.