Thousands of people could be left out of the census because of problems enumerators have in accessing apartment buildings and gated communities.
The Central Statistics Office (CSO) said the problems relating to such dwellings are more pronounced than in 2011.
Some 149,000 people were listed as living in apartment blocks in the last census, 55,000 of them in Dublin city.
Census forms have to be hand delivered by enumerators and must, by law, be filled out by all citizens.
CSO senior statistician Deirdre Cullen said complaints had come back from enumerators about getting access to apartment blocks, but she did not know the reasons why the problem appeared to be worse than five years ago.
“I am calling on the managers of these developments to co-operate with the census enumerators,” Ms Cullen said. “Residents of apartment blocks are advised to address the issue with the manager if they have not yet received their census form.” She said they were confident they would get at least 99 per cent of the population as they did in 2011. The census takes place on the night of April 24th.
