Atheists have launched a campaign to change the Census.
They want religious questions to be made optional and an end to the 'tick the box' format.
They say less people would claim to be Catholics if they had to write down their chosen faith.
They have submitted their suggestions to the Census advisory group.
Michael Nugent, the chairman of Atheist Ireland, said: "The purpose of the census should be to find the most accurate information and there is a science to designing questionnaires to do that.
"And one of the basic principles is that you don't build into the question something that is going to prompt people to answer in a certain way, because that is going to prejudice the outcomes.
"Well the question is first of all is 'what is your religion?'. That assumes that you have a religion."